I finally had the chance to read the long-waited NHibernate in Action, and I must say I am not very excited about it.
Covering just NHibernate 1.2, the book is, of course, extremely outdated. It does not cover any of the new features, and, what's worse, it does not cover well some of the old features, for example, there is no HQL reference, which I think it's a shame, although it is somewhat referred in chapter 7, nor there is a reference to some other projects, such as NHibernate Validator.
What matters is that if a developer wants to use NHibernate 2.x in a new project, he/she will find the information in this book inaccurate and misleading - NHibernate now supports SQL Server's TIMESTAMP data type for optimistic concurrency, for example, there is the NHibernate Burrow project to support long conversations, NHibernate Validator for validations, there is support for TransactionScope, <many-to-any> mappings, query-only properties, multi-queries, to name just a few.
The book does a fair job in introducing NHibernate, but I sincerely don't like the organization of it.