"Prototyping: A Practitioner's Guide" is a terrific and comprehensive review of both the prototyping process and the tools involved. There's really very little with which to find fault. I found that the book both validated my experience in prototyping and provided new techniques to try out, with many "Aha!" moments in both respects. The inclusion of case studies illustrating the techniques provide additional perspective and make the techniques more "real". The review of each prototyping technique/tool, whether paper or software-based, includes links to additional resources like toolkits, sample images, and the like - these would be especially useful to someone just getting started with a particular tool. Speaking as a designer who's typically relied on HTML prototypes and Visio, I must say my interest in Adobe Fireworks and, to a lesser extent, Axure is piqued. I think any UI/UX/IX designer, of any level of experience, would get something out of this book. Not that it would be useful only to them - analysts and software engineers will benefit from it as well.
A few very small issues:
* Early in the book, Mr. Warfel defines wireframes. I personally don't see why a wireframe can't depict flow - to me a wireframe is just a basic representation of the UI used to depict basic layout, flow, and interaction patterns. So, I think we simply differ slightly on the definition. I do like the term "narrative prototype" better and may start using that in place of "wireframe" - it is more descriptive.
* One issue with using common backgrounds in Visio prototypes is that you can't do a "select all" and then copy + paste the result into documentation, as all the background elements won't be copied. You can do a screen cap - but that takes a bit longer. So, just something to be aware of when using Visio.
* The author asks what is the point of using a virtual machine + Windows-only prototyping tools on a Mac. I'd say the point is simply that if, you do only own a Mac or Linux-based machine, you don't have to purchase an additional computer. Just a matter of practicality really.
* In the usability section - the author talks about the testing tool Morea, meaning "Morae" - a Techsmith product.
Again, these are small issues in an otherwise terrific book!