You're probably asking in the wrong thread, but here's what worked for me for Delta, in order of helpfulness:

1) Aerodynamics for the Naval Aviator (only the turbojet engine section...20 pages or so).
2) Mental Math for Pilots by Ronald D. McElroy
3) Ace the Technical Pilot Interview by Gary Bristow
4) Airline Pilot Interviews by Irv Jasinski
5) Checklist for Success by Cheryl Cage
6) Everything Explained for the Professional Pilot by Richie Lengel