Though the cover is from a later edition, this book was originally published in 1920, one of the many westerns that Max Brand wrote over the course of his life. (Brand died in 1944, while serving in the U.S. Army.) From the information that I found online, this book was about “Whistlin'” Dan Barry, a cowboy who only rode at night and whose horse was named Satan! That would be enough to keep me as far away from Whistlin’ Dan as possible!
The cover for this edition was done by John Leone.