I just upgraded my iPad and have the kindle app on both. My problem is that I have a lot of ebooks stored on my old iPad that were sent to me as advance reader copies via bookfunnel etc. that were copied to kindle. They show up in my kindle library on my old iPad but are not shown by Amazon in my digital content, so they don’t automatically transfer over. They only exist in my old iPad’s kindle library. Does anyone have any idea how I can get these types of ebooks transferred to my new iPad? I really don’t want to lose these books when I set my old iPad back to factory settings for resale. Any help would be appreciated. Thank you.
Personally I keep my entire library on calibre, which is installed on my PC, and I make regular backups to ensure the books remain safe.
Easy to move them back and forth between devices.
See Related post here calibre