Designing for the Web won't teach you anything about HTML5, CSS3 or anything else the cool kids are talking about these days. Quite the opposite. And this is why you should read it.
It takes a look back at the roots of graphic design and shows us why we shouldn't throw all that knowledge away, even though "the web is not print". Mark Boulton has a background from art- and design school, which he uses to explain the academics of typography, layout, colour theory and grids. For each theory he shows when and how this applies to the web, and even when to be crazy and break the rules to make it even better. Just make sure you learn the rules before you break them.
I really like this read since I'm already comfortable with the ins and outs of the typical front-end coding and web standards, but I have literately no education on the graphic design/art side of web design. I've leafed through a lot of books on the subject, even started reading a few, but none have had any connection to web design.
I recommend this book to anyone who touches any part of the design process. That includes you too, code-monkeys!