Books in iBooks on MacBook, iPad but not on iPhone
I have download 5 Harry Potter books from PottermoreShop and they have gone into my iBooks App on my MacBook Air. They are also on my iPad Air. When I open iBook on my iPhone 6 Plus its only show the first purchase, which was book 1 - 3 . I don't know how to get 4 & 5 to show and read on my iPhone. They were purchased awhile ago. I will admit I never read books on my iPhone. I had a situation recently that I thought I would continue reading the book I have been reading on my iPad on my iPhone, and was surprised it was not there. What am I doing wrong? With all the update recently, I haven't plugged my iPhone and or iPad into my computer to sync with iTunes for some time. I though that is what iCloud was for. Can anyone help me out?
iPhone 6 Plus, iOS 8.1