Engaging depending on your tastes. Some entries such as Britpop prove informative. Others, such as Freakbeat, Skate Punk, and Stoner Rock, too short to border on tautological or pointless in their lack of clarification. However, a brave attempt overall to connect the dots between your ears, as eclectic.
Not so much an encyclopedic guide as a blog in print. There's even a tongue-in-cheek section, micro-genres, which seems parodic. It included a Blogrock spin of its own, and appears to take the piss out of the seriousness with which some approach these taxonomies and definitions, hundreds at a time. But if you're totally unfamiliar with a particular category, whether or not you'll finish the few paragraphs or few hundred words (the depth varies greatly) with a better understanding's open.
Even before you get out of the first letter, a fine instance of art rock and another of Americana regions enlivens the content. And there's connections between if not cross-references, than at least artists of worth who can be found straddling boundaries, with some clever choices revealing King's impressive range of references. Not all of this can be streamed, however, and a lot, of course, will linger obscure. So it's what you'd expect, a hodgepodge of influences, quirks, and "trainspotting."