I believe this book is a great book for knowledgeable beginners or intermediates looking for a fast track into HTML for mobile beyond the basics, e.g., full-featured mobile web apps.
To me, the most striking feature of this book is how the authors cover so much material in such a powerful step-by-step fashion. The structure of the book is very elegant in leading the reader up a mountain with many steps (coding examples), perfectly placed plateaus (self-contained chapters), and satisfying views (very practical and useful content). I love how so many topics (basic HTML ... CSS ... jQuery ... mobile interfaces ... native device feature support ... and native app support (PhoneGap)) are interwoven so smoothly and progressively. The book covers a lot of ground while making it seem like an easy trek, but it's really a quite steep learning trajectory made to feel simple and easy. The chapter titles lay out the climb clearly, and some chapters (e.g., Chapter 5 "Using Device Features from Web Apps") contain some pleasant surprises along the way (e.g., geolocation, offline web app use, etc.). The journey is both delightful and fruitful.
I have not tried the code yet, but I feel quite confident it will work as expected. Another striking feature of the book is that it was written by three authors but feels like it's written by one extremely experienced web dev author. The authors, the editors, and the publisher have done a superb job meshing all the text into one cohesive whole.
The authors also do not jump blindly onto the HTML5 bandwagon, but seem to take a very practical and measured approach to new technologies. The one "big" technology they assume is jQuery (not jQuery Mobile). They refer to the others in passing and, while not dismissive, avoid them due to lack of adoption. Also, jQuery can be used for desktop as well. Everything (including UI) they build along the way... so it's a very thorough learning experience for anyone appreciative of seeing a web application from the ground up (again, modulo jQuery), skillfully avoiding and bypassing technical hurdles, and touching on the reasoning behind the technical decisions along the way.
One big advantage of the focus on mobile web apps is that the authors deftly sidestep many of the past issues of browsers (e.g., old PCs running ancient IE browsers). Instead the authors focus on a modern baseline of technology, provide cutting-edge optional techniques, and (when appropriate) focus on performance challenges. While I don't have web-dev experience to validate their judgement calls, they seem to know what they're doing. If so, this book is a treasure trove of wisdom and a very good starting point for pragmatic mobile web development.
Bottom line: If you're interested not just in mobile web development, but in mobile web apps... with native features... and even native apps based on web apps (i.e., PhoneGap), this book provides a smoothly accelerated journey that will fast track you through the technical milestones to your ultimate destination, web apps way beyond the basics. Highly recommended.