Thanks to web algorithms, there's a book blog list that is based on 20 ranking factors and includes Bookslut, Booking Mama, Bookgeeks, and many other book blogs / book websites (scroll for the various ranking lists): Top 50 Book Blogs.
The editors of the Millions webpage started to put together listings of literary tumblrs, there are 65 included now: The Millions Guide to Literary Tumblrs
For an unranked yet more adventurous approach, try the following topic/tag-links of Wordpress and Tumblr, each creates an automatic blog post stream for each tag:
- book posts at wordpress
- book posts at tumblr
- e-book posts at wordpress
- e-book posts at tumblr
- book reviews at tumblr + "reading"