For further information on the genetic algorithm and its applications in procedural content generation, you can check out the following material:
- Artificial Intelligence: A Modern Approach (third edition), Stuart Russel, Peter Norvig (2010), Prentice Hall.
- Procedural Content Generation in Games: A textbook and an overview of current research, Noor Shaker, Julian Togelius, and Mark J Nelson (2016). Springer. ISBN 978-3-319-42714-0. (http://pcgbook.com)