Originally Posted by Bob Butler
Has anyone been able to get this working with the Kindle app on an iPad?
I have never had syncing for non-Amazon books work correctly on the iPad when using iTunes to load the documents. My guess is that the Kindle app intercepts the files and ensures they go in as personal documents and not books, and that the iPad app only does Whispersync for books. If I use iExplorer to put the files on the iPad (to the Apps/Kindle/Library/eBooks folder instead of to Apps/Kindle/Documents), it does sync as long as there is an ASIN of some type. If the ASIN is an Amazon ASIN, the Book Extras also work.
I appreciate Kovid's stance on writing Amazon ASINs as opposed to using a UUID, but my preference is to use Amazon's ASINs if possible.
To date I've been using mobi2mobi to set ASINs to the Amazon one if the calibre UUID isn't sufficient for me, then iExplorer to actually copy the files to the iPad. For my Kindle Fire and Android phones I just put the files in the right directory. My nerdvana would be to have calibre write the Amazon ASIN for me, even if I have to use iExplorer to make sure the files don't get re-worked by iTunes. I'm toying around with letting that be my first foray into calibre plugin creation. I figure it would be nice to have some type of plugin to set the ASIN, either by looking it up or grabbing it from a custom attribute.