I have not made it through the whole book, but my first impressions are really good. One of the interfaces we were designing for work is to time consuming to wait for a http response, in the first chapter of this book it gives you the way to do Asynchronous requests correctly with rest.
There is also some good information on presenting resources that are not nouns, nouns are easy right you have a collection of people for example, you want to list all the people and do CRUD operations on a particular person. This to me is classical rest and is strait forward to do, but what about verbs (not in the POST, DELETE http sense) but in the give me driving directions sense. The book covers this and actually uses driving directions as it's example.
There are a couple of issues I'm still trying to find covered in the book, like how to do pagination on a collection of resources correctly. There is at least one recipe on this, but I did not see how to indicate a default page size (ie I requested all user accounts, but only returned first 200 dues to size, how does the client know that 200 were returned)
The other thing is the proper way to use http get parameters in search and other limiting operations. It would be nice to have some basic recipes there, but to be fair I might just not have seen them yet.
All in all it's a nice addition to your technical library.