Well this is a bit difficult to get my head around but some advice:
Map out your relationships visually and spent time on it, getting things right at the start is crucial to avoid major problems down the road. Some tools you can use are Visio (Microsoft) or Gliffy, I’m sure there are plenty of others.
Secondly I think if you should be using Taxonomies for the majority of these relationships.
I don’t know what book excerpts or praise is but if it is data tied to one specific book then it should be a custom meta field. You can have unlimited fields for the same meta keys.
I would consider not using any third party plugins for custom fields or taxonomies, create your own plugin to register them, there is now even on online CPT generator you can use and just copy/paste.
I also recommend checking out this post, even though it is dated, it might give you a good idea on how to arrange taxonomies, http://justintadlock.com/archives/2009/06/04/using-custom-taxonomies-to-create-a-movie-database