If I was to describe this book in five words, the review title says it all.
As an early (but not as early as Bruce or Remy) adopter of HTML5, I know a fair bit about the subject matter but after reading this book I realised how much I didn't know. As well as talking about the well known new features of HTML5 such as video, audio, canvas and forms, Bruce and Remy also delve into such diverse topics as ARIA (for accessibility), data storage, offline applications, the (nasty) drag and drop API and even the geolocation API (even though it's not strictly part of HTML5).
The book is littered with clear explanations and well written, amusing, sometimes weird, coding examples. There is no glossing over the fact that HTML5 is far from perfect, and that the HTML5 specification itself isn't finalised and therefore subject to change but the authors do a great job of keeping the content interesting and fresh.
It's a refreshing and honest approach to a technical book and one I highly recommend to web developers either new to the world of HTML5 or wanting to find out more.