For basic fatigue theory and applied info, try
1. Fundamentals of Metal Fatigue by Bannantine, Handrock & Comer
2. Fatigue Testing and Analysis by Lee, Pan, Hathway & Barkey
The first is out-of-print so try looking on bookfinder.com. The book starts with this is stress and goes through strain-life, crack growth and basic fracture mechanics. The second is relatively new from Elsevier. It also has a more diverse level of info including the first good explanation I've ever seen for how to use the double linear damage rule.
About the only basic topic missing from both books is how to create a statistically valid fatigue curve from raw test data, but I've yet to see a good textbook section or journal paper on that subject.
Doug