There is already one superb .NET Micro Framework book available (the one wot I helped to write) but now there is another.
Expert .NET Micro Framework by Jens Kuhner is excellent. It is written for those who want to really find out how to use all the features of the framework.
Whereas our book is more of an introduction to the field the Expert book, as the name implies, goes into more detail on the various class libraries and how you can use them. It also has the benefit of having been published a year or so later, and so has more up to date detail on the platforms that are now available. The people "lucky" enough to be at my session yesterday all got a free copy of the book (which really put a spring in their step) and they will find it very useful.
If you are serious about the framework you should get this book. If you are not serous about the framework you should this book and become serious about it.