There are two really good books based on the Joy Aylor case. The first one was used as a basis for the movie.
The movie was based on the book Open Secrets by Carlton Stowers. It is a very interesting and detailed read. You can order the book directly from the picture below. The woman on the front cover is the real Faith Kelsey aka Joy Aylor.
The other book about the case is just as compelling. It To Hatred Turned: A True Story of Love and Death in Texas by Ken Englade.
The case was also covered in True Detective Magazine
