(Full disclosure - this review is part of the Books for Bloggers program)
HTML5: The Missing Manual, by Matthew MacDonald, is a reference book that every web developer should have on their shelf. If you do any web development or think you might want to, get this book.
In HTML5: The Missing Manual, MacDonald gives a breif history of HTML and how it fits into the current view of the web. He then provides an extremely thourough explanation of the various elements that comprise HTML5. The handy dandy outline tells you what to expect: how HTML5 came to be, semantic elements, microdata & semantic add-ons, web forms, video & audio playback, CSS3, CSS3 media queries/responsive design, canvas, local storage, HTML5 caching, communication with a webserver (including websockets), and geolocation.
It's quite a list, but it's really quite a book. HTML5: The Missing Manual lives up to its name - a very well written manual for HTML5 that will help you get the most out of your web development time.
I give this book 5/5.