I often check Amazon to find out the pub date, if all else fails.
IMHO, I don't think you are wasting your time getting both books. The HTML5/CSS3 one will build on the first by introducing more of the latest CSS/HTML features. The latest Build your Own version gives a brief into to HTML5 and CSS3, but obviously doesn't cover nearly as much as the book dedicated to these topics.
Of course, all of the info is also available online, just not in such a structured way.