Hello I believe that you should cut epub file in parts like PDF. This one file is almost unreadable for most of readers like Pocketbook or Kindle (after convert to mobi). When i open on PocketBook Inkpad 3 it shows me that file have 5500+ pages, even start to change pages is really difficuld for device. I think on tablets it's not a big problem because CPU in them are faster. Thanks a lot for your work and response Michał Listowski