diff --git a/Source/VersOne.Epub.NetCoreDemo/VersOne.Epub.NetCoreDemo.csproj b/Source/VersOne.Epub.NetCoreDemo/VersOne.Epub.NetCoreDemo.csproj
index 670dccf..4d7c763 100644
--- a/Source/VersOne.Epub.NetCoreDemo/VersOne.Epub.NetCoreDemo.csproj
+++ b/Source/VersOne.Epub.NetCoreDemo/VersOne.Epub.NetCoreDemo.csproj
@@ -1,7 +1,7 @@
 <Project Sdk="Microsoft.NET.Sdk">
     <PropertyGroup>
         <OutputType>Exe</OutputType>
-        <TargetFramework>netcoreapp1.0</TargetFramework>
+        <TargetFramework>net5.0</TargetFramework>
         <RuntimeIdentifiers>win10-x64</RuntimeIdentifiers>
         <Authors>vers</Authors>
         <Company />
diff --git a/Source/VersOne.Epub.WpfDemo/Controls/BookHtmlContent.cs b/Source/VersOne.Epub.WpfDemo/Controls/BookHtmlContent.cs
index 8fb9aa8..1d89c25 100644
--- a/Source/VersOne.Epub.WpfDemo/Controls/BookHtmlContent.cs
+++ b/Source/VersOne.Epub.WpfDemo/Controls/BookHtmlContent.cs
@@ -76,6 +76,8 @@ protected override void OnStylesheetLoad(HtmlStylesheetLoadEventArgs e)
             string styleSheetFilePath = GetFullPath(HtmlContentFile.HtmlFilePath, e.Src);
             if (HtmlContentFile.StyleSheets.TryGetValue(styleSheetFilePath, out string styleSheetContent))
             {
+                // remove font-family? due to IndexOutOfRangeException in TheArtOfDev.HtmlRenderer.Core.Parse.CssParser.ParseFontFamilyProperty(string)
+                styleSheetContent = styleSheetContent.Replace("font-family", "delete-font-family");  // make it invalid
                 e.SetStyleSheet = styleSheetContent;
             }
             base.OnStylesheetLoad(e);
@@ -136,7 +138,7 @@ private string GetFullPath(string htmlFilePath, string relativePath)
                 basePath = Path.GetDirectoryName(basePath);
             }
             string fullPath = String.Concat(basePath.Replace('\\', '/'), '/', relativePath);
-            return fullPath.Length > 1 ? fullPath.Substring(1) : String.Empty;
+            return fullPath.TrimStart('/');
         }
 
         private void RegisterFonts()
diff --git a/Source/VersOne.Epub/Readers/BookCoverReader.cs b/Source/VersOne.Epub/Readers/BookCoverReader.cs
index 498b71c..1b0e23a 100644
--- a/Source/VersOne.Epub/Readers/BookCoverReader.cs
+++ b/Source/VersOne.Epub/Readers/BookCoverReader.cs
@@ -8,6 +8,21 @@ namespace VersOne.Epub.Internal
 {
     internal static class BookCoverReader
     {
+        public static EpubByteContentFileRef ReadBookCoverVersion3(EpubSchema epubSchema, Dictionary<string, EpubByteContentFileRef> imageContentRefs)
+        {
+            // https://ebookflightdeck.com/handbook/coverimage
+
+            var manifestItem = epubSchema.Package.Manifest.FirstOrDefault(m => m.Properties != null && m.Properties.Contains(ManifestProperty.COVER_IMAGE));
+            if (manifestItem == null)
+                return null;
+
+            EpubByteContentFileRef coverImageContentFileRef;
+            if (manifestItem.Href != null && imageContentRefs.TryGetValue(manifestItem.Href, out coverImageContentFileRef))
+                return coverImageContentFileRef;
+
+            return null;
+        }
+
         public static EpubByteContentFileRef ReadBookCover(EpubSchema epubSchema, Dictionary<string, EpubByteContentFileRef> imageContentRefs)
         {
             List<EpubMetadataMeta> metaItems = epubSchema.Package.Metadata.MetaItems;
diff --git a/Source/VersOne.Epub/Readers/ContentReader.cs b/Source/VersOne.Epub/Readers/ContentReader.cs
index f5d329f..5ab5c8d 100644
--- a/Source/VersOne.Epub/Readers/ContentReader.cs
+++ b/Source/VersOne.Epub/Readers/ContentReader.cs
@@ -70,7 +70,11 @@ public static EpubContentRef ParseContentMap(EpubBookRef bookRef)
                         break;
                 }
             }
-            result.Cover = BookCoverReader.ReadBookCover(bookRef.Schema, result.Images);
+
+            result.Cover = BookCoverReader.ReadBookCoverVersion3(bookRef.Schema, result.Images);  // try V3 first
+            if (result.Cover == null)
+                result.Cover = BookCoverReader.ReadBookCover(bookRef.Schema, result.Images);
+
             return result;
         }
 
diff --git a/Source/VersOne.Epub/Readers/NavigationReader.cs b/Source/VersOne.Epub/Readers/NavigationReader.cs
index 805c96e..841fa81 100644
--- a/Source/VersOne.Epub/Readers/NavigationReader.cs
+++ b/Source/VersOne.Epub/Readers/NavigationReader.cs
@@ -18,7 +18,14 @@ public static List<EpubNavigationItemRef> GetNavigationItems(EpubBookRef bookRef
             }
             else
             {
-                return GetNavigationItems(bookRef, bookRef.Schema.Epub3NavDocument);
+                if (bookRef.Schema.Epub3NavDocument != null)
+                    return GetNavigationItems(bookRef, bookRef.Schema.Epub3NavDocument);
+
+                // otherwise fallback to Epub2Ncx
+                if (null != bookRef.Schema.Epub2Ncx)
+                    return GetNavigationItems(bookRef, bookRef.Schema.Epub2Ncx);
+                else
+                    return new List<EpubNavigationItemRef>(); // if Ncx is missing, return an empty list
             }
         }
 
diff --git a/Source/VersOne.Epub/Readers/SchemaReader.cs b/Source/VersOne.Epub/Readers/SchemaReader.cs
index 32a7e4d..aceccb1 100644
--- a/Source/VersOne.Epub/Readers/SchemaReader.cs
+++ b/Source/VersOne.Epub/Readers/SchemaReader.cs
@@ -1,4 +1,5 @@
-using System.IO.Compression;
+using System;
+using System.IO.Compression;
 using System.Threading.Tasks;
 using VersOne.Epub.Schema;
 
@@ -15,7 +16,14 @@ public static async Task<EpubSchema> ReadSchemaAsync(ZipArchive epubArchive)
             EpubPackage package = await PackageReader.ReadPackageAsync(epubArchive, rootFilePath).ConfigureAwait(false);
             result.Package = package;
             result.Epub2Ncx = await Epub2NcxReader.ReadEpub2NcxAsync(epubArchive, contentDirectoryPath, package).ConfigureAwait(false);
-            result.Epub3NavDocument = await Epub3NavDocumentReader.ReadEpub3NavDocumentAsync(epubArchive, contentDirectoryPath, package).ConfigureAwait(false);
+            try
+            {
+                result.Epub3NavDocument = await Epub3NavDocumentReader.ReadEpub3NavDocumentAsync(epubArchive, contentDirectoryPath, package).ConfigureAwait(false);
+            }
+            catch (Exception ex)
+            {
+                result.Epub3NavDocument = null;
+            }
             return result;
         }
     }