"First Light" - Geoffrey "Boy" Wellum
I'll second that - an excellent read
Once again I'll plug Sandy Woodwards account of the Falklands conflict - 100 Days. That first chapter...
I know the whole Vietnam thing has probably been overdone, but I'd recommend John Del Vecchio's book "The 13th Valley". The accounts of the tension of fighting in the jungle are peerless IMO.
I've just finished Anthiny Beevor's book Stalingrad, which also was excellent. The suffering endured by the troops on both sides was unimaginable.