diff --git a/Emby.Server.Implementations/Library/Resolvers/Books/BookResolver.cs b/Emby.Server.Implementations/Library/Resolvers/Books/BookResolver.cs
index 0b93ebeb81..503de0b4e9 100644
--- a/Emby.Server.Implementations/Library/Resolvers/Books/BookResolver.cs
+++ b/Emby.Server.Implementations/Library/Resolvers/Books/BookResolver.cs
@@ -11,7 +11,7 @@ namespace Emby.Server.Implementations.Library.Resolvers.Books
 {
     public class BookResolver : MediaBrowser.Controller.Resolvers.ItemResolver<Book>
     {
-        private readonly string[] _validExtensions = { ".pdf", ".epub", ".mobi", ".cbr", ".cbz", ".azw3" };
+        private readonly string[] _validExtensions = { ".azw", ".azw3", ".cb7", ".cbr", ".cbt", ".cbz", ".epub", ".mobi", ".opf", ".pdf" };
 
         protected override Book Resolve(ItemResolveArgs args)
         {