Prion and Bloom are not intended as a primer on genetic programming principles. The user of these libraries is expected to come to the table with some rudimentary understanding of genetic and evolutionary perspective from a computing point of view (true biological understanding can be helpful in some cases, but is not always a full analog).

Below I have highlighted some books and resources that will give the beginner the basics necessary to utilize the Prion and Bloom GPL libraries in their own projects/research/modeling. I think a great start is the "A Field Guide to Genetic Programming". It covers all the basics. It is freely available online (although I would recommend purchasing a copy to support the contributors) and can be found here

Another good resource is the book Programming Collective Intelligence: Building Smart Web 2.0 Applications. This book, while not extensively focused on GP does have a chapter or two of extremely relevant material that is very well explained by the author. 

If you want to make the deeper dive, the following books may also be of interest (if a tad hard to find/expensive):

 

There are four books on GP written by Koza in the seminal series, however, I don't strongly recommend III and IV. They are good books, but they delve into domains that may not be of global interest. The first two focus on the basics of the approach (utilizing Lisp and tree-based program generation in book I and the expansion of the materials in book II focus on ADFs).

If you can pick up only one of the "deeper dive" books, I would recommend the Morgan Kaufmann Series entry.