I have actually been planning to buy this book for quite some time. Do you know when you'll be able to complete this book?
As we generally use JPA/Hibernate along with say Spring Framework in real life projects, would it be possible for you to include chapter on Spring/JPA integration and possible strategies for DAO layer testing?
I have two more chapters for the second part: Caching and Concurrency Control, and then a short part on jOOQ.
I'm not sure how much that will take because it implies doing some corrections after I get more reviews.
The good thing about Leanpub is that you can get the book know and get any update for free.
The book is not focused on Spring because the actual tuning happens in Hibernate, JDBC, and the DB part.
Related to testing, there is going to be an article on my blog next week, so better subscribe to my newsletter.