iBook sync with iphone 5 and iPad Air

if the books are from app store they will if they are some you add manually you need to sync with itunes

where you are in the book (book mark) are synced in iCloud

That sounds like you are looking at the Purchased tab in the iBooks app, that is part of the store and allows you to redownload books (if a book is only in the cloud then it will have the cloud icon against it instead of 'downloaded', tap on the cloud to download it) and/or look at their store description pages.

To read the books that show as 'downloaded' on that Purchased tab, tap the 'My Books' tab at the bottom left of the iBooks screen to go back to your bookshelf and you should see those books - tap on a book to open it. If you can't see your downloaded books on the bookshelf then tap the collection name at the top middle of the bookshelf and select 'All' or 'Books' collection instead.