I've written an ePub generator by using ZipArchive in .NET and looking at the spec (in Wikipedia) & a example.
It doesn't work! But I only get a generic error so I'm unable to fix anything from here.
Where could I go to upload my ePub and be told what is wrong with it? Or is there a tool that is better for it? I'm currently using Adobe ePub reader...
I found an online validator tool at https://www.epubconversion.com/epub-validator/.