Hibernate Made Easy is probably the best book you can find for getting started quickly with Hibernate and learning the basics properly and thoroughly. However, being the author, I might be a bit biased.
The Hibernate book by Gavin King is pretty much the reference guide. You need that one, but it's very comprehensive, which makes learning a bit of a challenge. Gavin's book as a reference, and Hiberante Made Easy to give you a jump start, is a pretty powerful combination.
Check out my signature links for some free tutorials on working with Hiberante.
Getting Started with Hibernate: A Simple Online Tutorial