danicca is correct. Apple does not allow iBooks to be used on any devices other than iDevices.
That alone is not so uncommon.
All Most distributors use DRM to limit the devices a book may be read on (this is a demand of many publishers though some do opt out), but... The DRM on Kobo books, Amazon books, Nook books Google books, can all be broken, thus allowing you to read your purchases freely; however, Apple seems to spend more money protecting iBooks than licensing content
and the iTunes tools were abandoned in disgust with the rationale that overall, few people actually buy books from Apple.
Now you know, you can avoid buying books in iBooks and any future purcases you make can be read on any device you want (sometimes with help from Apprentice Alf's tools --google him).
