Howdy Greenhorn!
Clearly, this is a bit of self-promotion, but many people have said that my book, Hibernate Made Easy, is both fun to read, and easy to understand. It goes from the basics, to the fundamentals, and then gets into advanced topics as well, such as the Criteria API, Advanced DAOs with Generics, and even two web based applications are created that wrap around Hibernate mappings and queries that you create in the book to show you how Hibernate gets used in practice.
Here's a little blurb on my website about both my book, and a few of the other books on the market that I believe are worth looking at as well.
The Best Books for Learning Hibernate and Object Relational Mapping
Regards!
-Cameron McKenzie