Moving beyond equilibrium, the text tackles selection. Key sub-topics include:
The "long story" short: This 1970 book is long out of print, and no legal, free PDF is widely available from the publisher (Blackburn Press has reprinted it, but sells it physically). However: an introduction to population genetics theory pdf
An Introduction to Population Genetics Theory - Google Books Moving beyond equilibrium, the text tackles selection
If the Crow and Kimura PDF proves too difficult or inaccessible, consider these modern alternatives (all legally available as eBooks): Moving beyond equilibrium