Java Persistence with Hibernate
Java Persistence with Hibernate was a good reference to me, but the book tries to be everything for everybody and this is what makes it a little hard to read. The book covers all the aspects of Hibernate framework in detail, starting from the ORM fundamentals up to conversational processing which is not found in any other Hibernate-related books.
As the name says, Hibernate Quickly is best suited as the introductory reference to Hibernate. The books follows the problem-solution pattern: at the beginning of each chapter, a bullet list of the topics is followed by the goals which a targeted by this chapter. This is what makes the book well-structured and easy to follow. I found a lot of easy to understand examples accompanied with good text explanations in this book and I think it is the best way to lean something new - by examples.