I really like the style of this book. It's written using a worked example, built up from first principles. I think this works really well because it gives the book a nice flow, and you see all the nuts and bolts in a logical order.
However, there are problems. As another reader mentioned, the book spends far too much time explaining Maven, which is unnecessary, and could be the subject of another book. Although the style is clear, with plenty of code examples, I do feel that this book skims the surface. It's ok as a gentle introduction to Hibernate, but the text uses the phrase "refer to Hibernate reference manual for more details" a bit too often.
I was also very disappointed to find that although there is much discussion about how to handle object associations, there appears to be absolutely no discussion of object inheritance. This is a fundamental concept of Object oriented programming, and I would expect any Hibernate book to explore the techniques used to persist object hierarchies.
On balance, if you are already familiar with Hibernate, this is probably not the book for you. However newcomers will learn a lot from it, and the style is very accessible. Just don't expect to find a comprehensive guide to Hibernate here.