Probably one of the best books four learning would be Manning Press, Hibernate in Action, although I don't know how up to date it is.
Hibernate is one of the oldest of the ORM systems and the original Hibernate syntax and support files were not the same as JPA syntax and support. However, Hibernate was one of the major contributors to the JPA standard, so the principles are very similar, even though the syntax varies. Also, Hibernate predated Java annotations, so the oldest Hibernate stuff used XML files to spec out the entities and stuff. XML is still an option, but it's no longer the only option.
I recommend JPA over straight (traditional) Hibernate. JPA is actually part of the official
EJB Version 3 ORM spec, though it can operate independently of EJB. I once migrated a project from Apache OpenJPA to Hibernate JPA in about 20 minutes when I had to work around an OpenJPA problem. Traditional Hibernate is doesn't offer flexibility like that.
I have an ancient copy of Hibernate In Action sitting right next to my Pro JPA 2 book. I will admit that I use the Pro JPA 2 book more, but then, it's been a long time since I learned ORMs. I started out on Kodo, which was also similar but not compatible, moved to Hibernate, then moved to JPA.