The only tool that removes Apple's iBooks Fairplay DRM is Requiem by Brahms version 3.3.6 and works with iTunes 10.5. Requiem 4.0 and later do not remove DRM from ebooks.
Requiem has a Tor website: http://tag3ulp55xczs3pn.onion. To reach the site using Tor, you will need to install Tor (http://www.torproject.org). If you're willing to sacrifice your anonymity, you can use the regular web with tor2web. Just go to http://tag3ulp55xczs3pn.tor2web.com.
Requiem is no longer developed as of 2012, with the last version 4.1.
Alternatively, you can download it from these download links:
You can download it from these download links:
Requiem 3.3.6 for Windows: http://www.datafilehost.com/download-f7916922.html