A good book is one that you read and re-read. Using this formula, my votes are...
Goodbye Micky Mouse - Robert Ludlum. Good tale with realistic characters and a few surprises/twists.
Chickenhawk - Robert Mason. A short flying career from the start of flight scool to Vietnam to demob and beyond.
Catch-22 - Joseph Heller. War and satire/irony at its finest. Absolutely brilliant.