diff --git a/backend/src/main/java/com/storycove/service/EPUBImportService.java b/backend/src/main/java/com/storycove/service/EPUBImportService.java
index 54536b1..0c0671a 100644
--- a/backend/src/main/java/com/storycove/service/EPUBImportService.java
+++ b/backend/src/main/java/com/storycove/service/EPUBImportService.java
@@ -481,18 +481,23 @@ public class EPUBImportService {
             return htmlContent;
         }
 
-        // Index all image resources by href and by bare filename for flexible lookup
+        // Index all image resources by href and by bare filename for flexible lookup.
+        // Also index resources whose media type epublib could not recognise (returns null for formats
+        // like WebP that are absent from its built-in type registry) by falling back to the href extension.
         Map<String, Resource> byHref = new HashMap<>();
         Map<String, Resource> byFilename = new HashMap<>();
         for (Resource resource : book.getResources().getAll()) {
-            if (resource.getMediaType() != null &&
-                    resource.getMediaType().toString().startsWith("image/")) {
-                String href = resource.getHref();
-                if (href != null) {
-                    byHref.put(href, resource);
-                    String filename = href.contains("/") ? href.substring(href.lastIndexOf('/') + 1) : href;
-                    byFilename.putIfAbsent(filename, resource);
-                }
+            String href = resource.getHref();
+            if (href == null) continue;
+
+            boolean isImageByMediaType = resource.getMediaType() != null &&
+                    resource.getMediaType().toString().startsWith("image/");
+            boolean isImageByExtension = hasImageExtension(href);
+
+            if (isImageByMediaType || isImageByExtension) {
+                byHref.put(href, resource);
+                String filename = href.contains("/") ? href.substring(href.lastIndexOf('/') + 1) : href;
+                byFilename.putIfAbsent(filename, resource);
             }
         }
 
@@ -530,7 +535,7 @@ public class EPUBImportService {
                 }
 
                 String mediaType = resource.getMediaType() != null ?
-                        resource.getMediaType().toString() : "image/jpeg";
+                        resource.getMediaType().toString() : getMediaTypeFromHref(resource.getHref());
                 String extension = getExtensionFromMediaType(mediaType);
                 String filename = "epub-img-" + System.currentTimeMillis() + "-" +
                         (int) (Math.random() * 100000) + "." + extension;
@@ -619,6 +624,32 @@ public class EPUBImportService {
                 return "jpg"; // Default fallback
         }
     }
+
+    /**
+     * Determine MIME type from the file extension in an EPUB resource href.
+     * Used as a fallback when epublib does not recognise the media type (e.g. WebP).
+     */
+    private String getMediaTypeFromHref(String href) {
+        if (href == null) return "image/jpeg";
+        String lower = href.toLowerCase();
+        if (lower.endsWith(".png"))  return "image/png";
+        if (lower.endsWith(".gif"))  return "image/gif";
+        if (lower.endsWith(".webp")) return "image/webp";
+        if (lower.endsWith(".svg"))  return "image/svg+xml";
+        return "image/jpeg"; // covers .jpg, .jpeg and unknown formats
+    }
+
+    /**
+     * Returns true if the href path ends with a known image file extension.
+     * Used to index EPUB resources whose media type epublib could not determine.
+     */
+    private boolean hasImageExtension(String href) {
+        if (href == null) return false;
+        String lower = href.toLowerCase();
+        return lower.endsWith(".jpg")  || lower.endsWith(".jpeg") ||
+               lower.endsWith(".png")  || lower.endsWith(".gif")  ||
+               lower.endsWith(".webp") || lower.endsWith(".svg");
+    }
     
     private ReadingPositionDto convertToDto(ReadingPosition position) {
         if (position == null) return null;