Advanced Book Blocks
This module integrates with the API provided by theJQuery Menu module (version 1.8 and higher) to provide click and expand book menus with the ability to customize each block individually.
Not only can you set blocks to hold particular sets of books, but you can also set each block to enable new books on a per block level based on taxonomy terms which are assigned.
In other words, you can set a block to only add books that have been tagged with "foo" or you you can do the opposite and exclude only books that have been tagged with "bar". This makes it much easier to sort your books on your site on a per block level.
Version 1.2 has two important bug fixes, so if you are running 1.1 you should upgrade.