Michael E. Cohen, writing for TidBITS:

iBooks is not quite as unreliable and confusing as it was when I wrote about it last year, but neither has it improved nearly as much as loyal iBooks users deserve. Moreover, what little support documentation Apple provides is sketchy and inaccurate, leaving the impression that even the support and documentation departments within Apple are ignoring iBooks.

Cohen’s library may be an edge case with over 700 titles, but the problems he mentions are basic usability issues that should get fixed.