The first chapters give a good feel for the vocabulary, and some good techniques for implementing REST. A lot of the 'rules', especially those related to basic CRUD operations, are clean and simple with useful examples.
Unfortunately, the later chapters get more and more focused on specifying something called 'WRML', which is a concept/language newly introduced in this book as far as I can tell.
Personally I would recommend ignoring the sections dealing with WRML (or keep them in mind as a detailed example of one possible way of handling some of the REST issues).
As to WRML itself: yuck. It appears to be an attempt to drag in some of the unnecessary complexity of SOAP with little added benefit. Not recommended.
Overall: There is some definite value to be found in this book, just be wary and realize some of this is the author's attempt to 'create' a new standard as much as explain the current state of the art.