Free HTML5 & CSS3 Kindle Books
I haven't read these yet so I can't vouch for their quality, but thought I'd pass on the links while they're priced at $0:
Robin Nixon's HTML5 Crash Course: Learn HTML5 in 20 Easy Lessons
http://www.amazon.com/Robin-Nixons-HTML5-Course-ebook/dp/B005FCIVLS
Robin Nixon's CSS & CSS3 Crash Course
http://www.amazon.com/Robin-Nixons-Crash-Course-ebook/dp/B006PIW4IM
Can be read on PC/Mac with the free Kindle software of course.