diff --git a/src/NexusReader.Infrastructure/Services/BookStorageService.cs b/src/NexusReader.Infrastructure/Services/BookStorageService.cs
index 9af4ee5..d1f844f 100644
--- a/src/NexusReader.Infrastructure/Services/BookStorageService.cs
+++ b/src/NexusReader.Infrastructure/Services/BookStorageService.cs
@@ -27,6 +27,7 @@ public class BookStorageService : IBookStorageService
         var uploadsFolder = Path.Combine(_environment.WebRootPath, "uploads");
         EnsureDirectoryExists(uploadsFolder);
 
+        fileName = SanitizeFileName(fileName);
         var uniqueFileName = $"{Guid.NewGuid()}_{fileName}";
         var filePath = Path.Combine(uploadsFolder, uniqueFileName);
         
@@ -52,6 +53,7 @@ public class BookStorageService : IBookStorageService
         var coversFolder = Path.Combine(_environment.WebRootPath, "covers");
         EnsureDirectoryExists(coversFolder);
 
+        fileName = SanitizeFileName(fileName);
         var uniqueFileName = $"{Guid.NewGuid()}_{fileName}";
         var filePath = Path.Combine(coversFolder, uniqueFileName);
         
@@ -63,6 +65,25 @@ public class BookStorageService : IBookStorageService
         return $"covers/{uniqueFileName}";
     }
 
+    private string SanitizeFileName(string fileName)
+    {
+        if (string.IsNullOrEmpty(fileName)) return fileName;
+
+        var sanitized = fileName
+            .Replace('\u00A0', ' ')
+            .Replace('\u2007', ' ')
+            .Replace('\u200B', ' ')
+            .Replace('\u202F', ' ');
+
+        var invalidChars = Path.GetInvalidFileNameChars();
+        foreach (var c in invalidChars)
+        {
+            sanitized = sanitized.Replace(c, '_');
+        }
+
+        return sanitized;
+    }
+
     private void EnsureDirectoryExists(string path)
     {
         if (!Directory.Exists(path))
diff --git a/src/NexusReader.Infrastructure/Services/EpubReaderService.cs b/src/NexusReader.Infrastructure/Services/EpubReaderService.cs
index 6079d42..4154640 100644
--- a/src/NexusReader.Infrastructure/Services/EpubReaderService.cs
+++ b/src/NexusReader.Infrastructure/Services/EpubReaderService.cs
@@ -18,7 +18,7 @@ public class EpubReaderService : IEpubReader
     private readonly ILogger<EpubReaderService> _logger;
     private const int WordThreshold = 1000;
 
-    private static readonly Regex ImageTagRegex = new(@"<img\b(?<before>[^>]*?\bsrc=[""'])(?<src>[^""']*?)(?<after>[""'][^>]*?>)", RegexOptions.IgnoreCase | RegexOptions.Compiled);
+    private static readonly Regex ImageTagRegex = new(@"(?<before><img\b[^>]*?\bsrc=[""'])(?<src>[^""']*?)(?<after>[""'][^>]*?>)", RegexOptions.IgnoreCase | RegexOptions.Compiled);
     private static readonly Regex BodyMatchRegex = new(@"<body\b[^>]*>(.*?)</body>", RegexOptions.IgnoreCase | RegexOptions.Singleline | RegexOptions.Compiled);
     private static readonly Regex ParagraphMatchRegex = new(@"<(p|h[1-6]|ul|ol|blockquote|pre)\b[^>]*>.*?</\1>|<hr\b[^>]*>|<img\b[^>]*>", RegexOptions.IgnoreCase | RegexOptions.Singleline | RegexOptions.Compiled);
     private static readonly Regex StyleScriptRegex = new(@"<(style|script)\b[^>]*>.*?</\1>", RegexOptions.IgnoreCase | RegexOptions.Singleline | RegexOptions.Compiled);
@@ -27,6 +27,9 @@ public class EpubReaderService : IEpubReader
     private static readonly Regex ImgTagSanitizerRegex = new(@"<img\b[^>]*>", RegexOptions.IgnoreCase | RegexOptions.Compiled);
     private static readonly Regex SrcAttributeRegex = new(@"\bsrc=[""'](?<src>[^""']*)[""']", RegexOptions.IgnoreCase | RegexOptions.Compiled);
     private static readonly Regex AltAttributeRegex = new(@"\balt=[""'](?<alt>[^""']*)[""']", RegexOptions.IgnoreCase | RegexOptions.Compiled);
+    private static readonly Regex SvgImageTagRegex = new(@"<image\b(?<attrs>[^>]*?)>", RegexOptions.IgnoreCase | RegexOptions.Compiled);
+    private static readonly Regex HrefAttributeRegex = new(@"\b(xlink:)?href=[""'](?<href>[^""']*)[""']", RegexOptions.IgnoreCase | RegexOptions.Compiled);
+    private static readonly Regex EmptyBlockRegex = new(@"^(</?(p|h[1-6]|ul|ol|li|blockquote|pre|div|span|br)\b[^>]*>|&nbsp;|\s)*$", RegexOptions.IgnoreCase | RegexOptions.Compiled);
 
     public EpubReaderService(
         IDbContextFactory<AppDbContext> dbContextFactory,
@@ -102,7 +105,7 @@ public class EpubReaderService : IEpubReader
             foreach (var p in paragraphs)
             {
                 var sanitizedContent = SanitizeParagraph(p);
-                if (string.IsNullOrWhiteSpace(sanitizedContent)) continue;
+                if (string.IsNullOrWhiteSpace(sanitizedContent) || EmptyBlockRegex.IsMatch(sanitizedContent)) continue;
 
                 blocks.Add(new TextSegmentBlock($"seg-{blockCounter++}", sanitizedContent));
 
@@ -236,7 +239,9 @@ public class EpubReaderService : IEpubReader
     {
         if (string.IsNullOrEmpty(html)) return html;
 
-        return ImageTagRegex.Replace(html, match =>
+        var normalizedHtml = NormalizeSvgImageTags(html);
+
+        return ImageTagRegex.Replace(normalizedHtml, match =>
         {
             var rawSrc = match.Groups["src"].Value;
             
@@ -258,6 +263,31 @@ public class EpubReaderService : IEpubReader
         });
     }
 
+    private static string NormalizeSvgImageTags(string html)
+    {
+        if (string.IsNullOrEmpty(html)) return html;
+
+        return SvgImageTagRegex.Replace(html, match =>
+        {
+            var attrs = match.Groups["attrs"].Value;
+            
+            if (SrcAttributeRegex.IsMatch(attrs))
+            {
+                return $"<img {attrs}>";
+            }
+            
+            var hrefMatch = HrefAttributeRegex.Match(attrs);
+            if (hrefMatch.Success)
+            {
+                var hrefVal = hrefMatch.Groups["href"].Value;
+                var cleanedAttrs = HrefAttributeRegex.Replace(attrs, "");
+                return $"<img src=\"{hrefVal}\" {cleanedAttrs}>";
+            }
+            
+            return match.Value;
+        });
+    }
+
     private static string ResolveRelativePath(string basePath, string relativePath)
     {
         if (string.IsNullOrEmpty(relativePath)) return string.Empty;
diff --git a/src/NexusReader.UI.Shared/Components/Organisms/ReaderCanvas.razor.css b/src/NexusReader.UI.Shared/Components/Organisms/ReaderCanvas.razor.css
index 604e35c..4456cdb 100644
--- a/src/NexusReader.UI.Shared/Components/Organisms/ReaderCanvas.razor.css
+++ b/src/NexusReader.UI.Shared/Components/Organisms/ReaderCanvas.razor.css
@@ -45,7 +45,7 @@
     min-height: calc(100vh - 180px);
     display: flex;
     flex-direction: column;
-    gap: 1.5rem;
+    gap: 0.75rem;
     position: relative;
     padding: 3rem 4rem 15rem 4rem;
     /* Large padding-bottom for reachability, plus comfortable side margins */
@@ -69,10 +69,21 @@
 .block-wrapper {
     transition: all 0.5s ease;
     border-radius: 8px;
-    padding: 8px;
+    padding: 2px 8px;
     border: 1px solid transparent;
 }
 
+/* Pull subsequent block closer to headings or bold exercise labels */
+.block-wrapper:has(h1),
+.block-wrapper:has(h2),
+.block-wrapper:has(h3),
+.block-wrapper:has(h4),
+.block-wrapper:has(h5),
+.block-wrapper:has(h6),
+.block-wrapper:has(p > strong) {
+    margin-bottom: -0.25rem;
+}
+
 /* Typographic refinement for TextSegmentBlock */
 ::deep .nexus-ebook {
     font-family: 'Merriweather', serif !important;
@@ -90,12 +101,24 @@
     /* Warm charcoal for legibility */
 }
 
+/* Reset default margins for elements within separate block-wrappers */
+::deep .nexus-ebook p,
+::deep .nexus-ebook h1,
+::deep .nexus-ebook h2,
+::deep .nexus-ebook h3,
+::deep .nexus-ebook h4,
+::deep .nexus-ebook h5,
+::deep .nexus-ebook h6 {
+    margin-top: 0 !important;
+    margin-bottom: 0 !important;
+}
+
 /* Callout Box styling for legacy blockquote segments */
 ::deep .nexus-ebook blockquote {
     background-color: rgba(255, 255, 255, 0.02);
     border-left: 4px solid var(--nexus-neon);
     padding: 1rem 1.25rem;
-    margin: 1.5rem 0 1.5rem 0;
+    margin: 1rem 0 1rem 0;
     border-radius: 0 8px 8px 0;
     font-size: 1.05rem;
     color: #e2e8f0;
@@ -116,7 +139,7 @@
     color: #e0e0e0;
     padding: 1.25rem;
     border-radius: 8px;
-    margin: 2rem 0;
+    margin: 1.25rem 0;
     overflow-x: auto;
     box-shadow: inset 0 2px 4px rgba(0, 0, 0, 0.1);
     border-left: 4px solid var(--nexus-neon);
@@ -353,7 +376,7 @@
         padding-left: 18px !important;
         padding-right: 18px !important;
         padding-bottom: 4rem;
-        /* Safe breathing room */
+        gap: 0.75rem !important; /* Tighter spacing on mobile */
     }
 }
 
@@ -367,8 +390,8 @@
     ::deep .nexus-ebook h1 {
         font-size: 1.35rem !important;
         line-height: 1.4 !important;
-        margin-top: 1.5rem !important;
-        margin-bottom: 1rem !important;
+        margin-top: 0.5rem !important; /* Tighter margins on mobile */
+        margin-bottom: 0.25rem !important;
     }
 }
 
@@ -580,4 +603,44 @@
         transform: rotate(0deg) scale(1);
         opacity: 1;
     }
+}
+
+/* Ebook Image Scaling, Alignment, and Separation Lines */
+.block-wrapper:has(img) {
+    border-top: 1px solid rgba(255, 255, 255, 0.08);
+    border-bottom: 1px solid rgba(255, 255, 255, 0.08);
+    padding: 1rem 0;
+    margin: 0.5rem 0;
+    display: flex;
+    justify-content: center;
+    align-items: center;
+    width: 100%;
+}
+
+.theme-light .block-wrapper:has(img) {
+    border-top: 1px solid rgba(0, 0, 0, 0.08);
+    border-bottom: 1px solid rgba(0, 0, 0, 0.08);
+}
+
+::deep .nexus-ebook img {
+    width: 100%;
+    max-width: 100%;
+    max-height: 75vh;
+    height: auto;
+    display: block;
+    border-radius: 8px;
+    box-shadow: 0 10px 30px rgba(0, 0, 0, 0.4);
+    border: 1px solid rgba(255, 255, 255, 0.1);
+    opacity: 0.9;
+    transition: opacity 0.25s ease;
+}
+
+::deep .nexus-ebook img:hover {
+    opacity: 1;
+}
+
+.theme-light ::deep .nexus-ebook img {
+    box-shadow: 0 10px 25px rgba(0, 0, 0, 0.12);
+    border: 1px solid rgba(0, 0, 0, 0.1);
+    opacity: 1;
 }
\ No newline at end of file
diff --git a/src/NexusReader.Web/Program.cs b/src/NexusReader.Web/Program.cs
index d3484d3..08d30bd 100644
--- a/src/NexusReader.Web/Program.cs
+++ b/src/NexusReader.Web/Program.cs
@@ -1,4 +1,5 @@
 using NexusReader.Web.Components;
+using Microsoft.AspNetCore.Authentication.JwtBearer;
 using Microsoft.AspNetCore.Mvc;
 using Microsoft.AspNetCore.Components;
 using NexusReader.Application;
@@ -121,6 +122,17 @@ builder.Services.AddAuthentication(options =>
         options.DefaultScheme = IdentityConstants.ApplicationScheme;
         options.DefaultSignInScheme = IdentityConstants.ExternalScheme;
     })
+    .AddJwtBearer(JwtBearerDefaults.AuthenticationScheme, options =>
+    {
+        options.Authority = builder.Configuration["Jwt:Authority"] ?? "https://example.com/";
+        options.Audience = builder.Configuration["Jwt:Audience"] ?? "NexusReaderAPI";
+        options.TokenValidationParameters = new Microsoft.IdentityModel.Tokens.TokenValidationParameters
+        {
+            ValidateIssuer = true,
+            ValidateAudience = true,
+            ValidateLifetime = true
+        };
+    })
     .AddGoogle(options =>
     {
         options.ClientId = builder.Configuration["Authentication:Google:ClientId"] ?? "placeholder-id";
diff --git a/tests/NexusReader.Application.Tests/Services/EpubReaderServiceTests.cs b/tests/NexusReader.Application.Tests/Services/EpubReaderServiceTests.cs
index 81609bf..8c960ca 100644
--- a/tests/NexusReader.Application.Tests/Services/EpubReaderServiceTests.cs
+++ b/tests/NexusReader.Application.Tests/Services/EpubReaderServiceTests.cs
@@ -267,6 +267,74 @@ public class EpubReaderServiceTests : IDisposable
         colonResult.Errors.First().Message.Should().Contain("Invalid resource path");
     }
 
+    [Fact]
+    public void RewriteImageUrls_PreservesImgPrefix()
+    {
+        // Arrange
+        var method = typeof(EpubReaderService).GetMethod("RewriteImageUrls", System.Reflection.BindingFlags.NonPublic | System.Reflection.BindingFlags.Static);
+        method.Should().NotBeNull();
+
+        var input = "<img class=\"epub_cover_page_img\" src=\"cover.jpg\" />";
+        var ebookId = Guid.NewGuid();
+
+        // Act
+        var result = (string)method.Invoke(null, new object[] { input, ebookId, "OEBPS/cover-page.xhtml" });
+
+        // Assert
+        result.Should().StartWith("<img class=\"epub_cover_page_img\" src=\"/api/epub/");
+    }
+
+    [Fact]
+    public void RewriteImageUrls_NormalizesSvgImageTags()
+    {
+        // Arrange
+        var method = typeof(EpubReaderService).GetMethod("RewriteImageUrls", System.Reflection.BindingFlags.NonPublic | System.Reflection.BindingFlags.Static);
+        method.Should().NotBeNull();
+
+        var inputXlink = "<image xlink:href=\"images/fig1.jpg\" width=\"100%\" />";
+        var inputHref = "<image href=\"images/fig2.jpg\" />";
+        var ebookId = Guid.NewGuid();
+
+        // Act
+        var resultXlink = (string)method.Invoke(null, new object[] { inputXlink, ebookId, "OEBPS/chapter1.xhtml" });
+        var resultHref = (string)method.Invoke(null, new object[] { inputHref, ebookId, "OEBPS/chapter1.xhtml" });
+
+        // Assert
+        resultXlink.Should().Contain("<img src=\"/api/epub/");
+        resultXlink.Should().Contain("width=\"100%\"");
+        resultXlink.Should().NotContain("<image");
+        resultXlink.Should().NotContain("xlink:href");
+
+        resultHref.Should().Contain("<img src=\"/api/epub/");
+        resultHref.Should().NotContain("<image");
+        resultHref.Should().NotContain("href=");
+    }
+
+    [Theory]
+    [InlineData("<p><br /></p>")]
+    [InlineData("<p>&nbsp;</p>")]
+    [InlineData("<p> <br>  </p>")]
+    [InlineData("<br>")]
+    [InlineData("&nbsp;")]
+    public void EmptyBlockRegex_MatchesEmptyBlocks(string input)
+    {
+        // Arrange
+        var field = typeof(EpubReaderService).GetField("EmptyBlockRegex", System.Reflection.BindingFlags.NonPublic | System.Reflection.BindingFlags.Static);
+        field.Should().NotBeNull();
+        var regex = (System.Text.RegularExpressions.Regex)field.GetValue(null);
+        regex.Should().NotBeNull();
+
+        var method = typeof(EpubReaderService).GetMethod("SanitizeParagraph", System.Reflection.BindingFlags.NonPublic | System.Reflection.BindingFlags.Static);
+        method.Should().NotBeNull();
+
+        // Act
+        var sanitized = (string)method.Invoke(null, new object[] { input });
+        var isMatch = regex.IsMatch(sanitized);
+
+        // Assert
+        isMatch.Should().BeTrue();
+    }
+
     public void Dispose()
     {
         _connection.Close();