diff --git a/api/src/app/services/book.service.ts b/api/src/app/services/book.service.ts
index 2980cb2..d279f2c 100644
--- a/api/src/app/services/book.service.ts
+++ b/api/src/app/services/book.service.ts
@@ -10,6 +10,7 @@ import {
   validateUrl,
   validateRating,
   validateStringLength,
+  validateDataUrl,
   MAX_LENGTHS,
 } from "../utils/validation";
 
@@ -44,9 +45,23 @@ export class BookService {
       throw new Error("Rating must be an integer between 0 and 10.");
     }
 
-    // Validate cover image URL
-    if (data.coverImage && !validateUrl(data.coverImage)) {
-      throw new Error("Invalid cover image URL. Only http and https URLs are allowed.");
+    if (data.coverImage) {
+      if (data.coverImage.startsWith("data:")) {
+        const sizeInBytes = data.coverImage.length * 0.75;
+        if (sizeInBytes > MAX_LENGTHS.IMAGE_DATA) {
+          throw new Error("Cover image must be under 5MB.");
+        }
+        if (!validateDataUrl(data.coverImage)) {
+          throw new Error("Invalid image data URL.");
+        }
+      } else {
+        if (!validateStringLength(data.coverImage, MAX_LENGTHS.URL)) {
+          throw new Error(`Cover image URL must be ${MAX_LENGTHS.URL} characters or less.`);
+        }
+        if (!validateUrl(data.coverImage)) {
+          throw new Error("Invalid cover image URL. Only http and https URLs are allowed.");
+        }
+      }
     }
 
     // Validate tags