I have lots of books on my iPad, that I purchased/downloaded on my ipad.

In iTunes I can see them all listed under Devices/Claire's iPad/Books.

Only some of them are appearing in Library/Books though. Some are books, some pdf's that appear, and I can't see a pattern as to why some appear and some don't.

I have transferred purchases from iPad to iTunes. "All Books" is selected when I try to sync.

When I do try to sync i get the message "The iPad “Claire’s iPad” is synced with another iTunes library. Do you want to erase this iPad and sync with this iTunes library?"

As the only place I have the books is on my iPad, I don't want to do this.

I did previously have my iTunes library on a pc, but thought I had successfully transferred it to my iMac. Syncing works fine on my iPhone.

Any suggestions?