'HTML & CSS in Simple Steps' will enable you to create accessible, standards-compliant, websites - equipping you with knowledge on theory, coding skills, and best practice needed to build Web pages.
I found it useful as a refresher if you already know the basics. But it wouldn't be useful to someone who already knows more than that, as it isn't comprehensive enough to be an actual reference manual.
As for being a tool for beginners, I'd deem it tricky as well. It points to some useful resources, but some of them aren't available directly anymore (like the ones at Veign, which you'd have to find through other means). It'd also benefit from a more task-oriented approach, such as a "build your first website" set of lessons in order to try what the different HTML tags and CSS combinators do.