No-one has mentioned "Sagittarius Rising" by Cecil Lewis, which I think must be the best book on what it was like to fly in WW1 and (to a civilian) the book which I felt gave me a real insight into what military flying might be about.
Maybe it's too distant from the modern airforce to be a good choice for current military pilots, but it certainly captured some of what I feel about my private flying in gliders and I've never read anything which captured the magic of flying so well.
(And, if anyone ever wants to talk down military pilots, the sheer level of human sacrifice described here should shut them up for ever)