Publishers Catheryn Kilgarriff and Rebecca Gillieron (of the independent Marion Boyars Press in London) have written what seems to be the first in-print guide to the ever-growing world of book blogs: The Bookaholics' Guide to Book Blogs. It is of necessity both tremendously selective and quite time-dependent; I suspect someone reading this even six months or a year from now may find its analysis and suggestions outdated.
In fairly short, breezy chapters, the authors discuss various sorts of book blogs (those written by publishers, authors, booksellers, as well as the many types of regular readers in various genres), the role of the Internet in literary criticism and the tension between print reviewers and bloggers. They also briefly discuss the online literary magazine phenomenon (Salon, McSweeney's, N+1), and (in what was one of the most interesting sections for me) examine the debates within the publishing industry about the role, staying power and importance of blogs in the grand scheme of things.
More analysis would have been welcome; the long excerpts from various blogs I didn't so much need. For anyone who's never read a book blog, or is interested in starting one and getting a sense of some of the issues surrounding them, this is a fairly interesting and possibly useful read. The list of mentioned blogs at the back may also be a handy resource (although some of the sites referenced there are already inactive). But for folks who already read blogs regularly, or write their own, it may not be entirely necessary.