This is a reasonably long book, at nearly 400 pages; it would be even longer if it weren't for the excessively large number of words per page. I found this book hard to read, in part due to the layout, and in part due to Scott's writing style. Though he is a stout member of the Agile camp, Scott clearly also believes in the benefit of repetition to get his message across; there is many a repeated phrase or sentence, and there is at least one whole paragraph repeated word-for-word. All this detracts from the book, which is unfortunate since Scott has many good things to say.
The book is divided into 5 parts. The first two parts cover the principles you should work to and practices you should be doing to say that you are doing Agile Modelling as Scott defines it. The values of Agile Modelling are the four values of eXtreme Programming, plus a fifth (Humility), and the principles and practices are then derived from applying these values to a modelling perspective. For example, the value of Courage leads one to Discard Temporary Models, and the values of Humility and Communication lead one to realise that Everyone Can Learn From Everyone Else, and that you should Model With Others. This description of the principles and practices forms the real meat of the book. Most (perhaps all) of what Scott says here is sensible advice that should be followed by anyone pursuing an Agile approach to software development.
The remaining parts describe the how Agile Modelling fits into XP and the Universal Process, with a discussion on introducing Agile Modelling into your process. This also includes a discussion of when Agile Modelling is not a good fit; a check list of things you must be doing to say you are Agile Modelling; and a list of things which you must not be doing if you want to say you are Agile Modelling. The book finishes off with an appendix listing a host of modelling techniques to consider when the need arises; Scott is quite clear that you need to Apply the Right Artefact, and having a wide range to choose from makes this easier since you are not stretching a model beyond what it can easily cover.
If you are interested in modelling, and want to know how it fits into Agile projects, or you are looking to make your current process more Agile by reducing unnecessary modelling work, then this book is well worth a read; I just wish it was easier to read. Recommended.