Just caught a tweet from @jwikert that led me to this: blog-rank's list of the top 50 book blogs. Blog-rank (spelled several different ways on its own page, btw) used 20 different factors to rank the blogs, including how many people subscribe in a reader, how many incoming links there are, and the blogs' popularity on social sites.
Joe himself is well represented at #14, and there are several others that I've got on my feeds. But what blows my mind is how many of them I hadn't heard of before (like, oh, the one with the #1 ranking). This either shows my spotty attention span, or it demonstrates just how darn many awesome book blogs there are. And Joe says he thinks they've missed a few.
At any rate, I guess I'll be putting a lot more on my feeds.