You might want to provide some more information as to your needs? Do you just want to learn more about the iPad as a user or as a potential app developer?
Also if not already done, go to Apple Support HERE - check out the headings to the left and also click on manuals - you can download the iPad2 manual pertaining to iOS 5 if that is on your device?
Finally, there are plenty of iPad 2 books (although many will not have the newest on the iOS 5 upgrade) - check Amazon if interested in that option - good luck!
If you have other Apple products or are interested in other Apple kit then why not join our sister forum too at http://www.appleforums.net/
Finally, if you still haven't had enough, how about a video explaining about our other forums (note:you may want to play this at half speed but hey, why shouldn't Phil be excited about our forums!)