iTunes 12.3
Apple has released iTunes 12.3 with support for the just-released iOS 9 (see “iOS 9: TidBITS Answers Your Questions,” 16 September 2015) and improved support for the still-to-come OS X 10.11 El Capitan. The update also improves Apple Music accessibility with VoiceOver, fixes a bug that prevented reordering of songs within Up Next, resolves an issue that prevented some radio stations from appearing within Recently Played, and rectifies a problem that prevented songs that you loved on an iOS device from appearing on iTunes. Additionally, iTunes adds support for Apple’s two-factor authentication. (Free, 239 MB via direct download or via Software Update, 10.7.5+)
I updated to iTunes 12.3 and 80% of my books are not showing on iTunes to sync with my iOS devices. Luckily my other computer still has iTunes12.2 - I managed to synced my book using iTunes 12.2. I started wondering if Apple is blocking non-books purchased from to sync with iOS devices or is just a bug