Question

What is the best eBook for a beginner in Hibernate?

Answer 1

The online Reference Documentation is a good place to start, especially the Hibernate 5 new User Guide.

And for the “absolute reference”, get Java Persistence with Hibernate (a revised edition of the old Hibernate in Action). Here is what the authors write about this book:

We had three goals when writing this
book, so you can read it as

• A tutorial for Hibernate, Java Persistence, and EJB 3.0 that guides
  you through your first steps with
  these solutions
• A guide for learning all basic and advanced Hibernate features for
  object/ relational mapping, object
  processing, querying, performance
  optimization, and application design
• A reference for whenever you need a complete and technically accurate
  definition of Hibernate and Java
  Persistence functionality

As stated, it’s the absolute reference (880 pages), it allows to go as deep as you want.

For tuning Hibernate, you could also check the High-Performance Java Persistence book.