[Robotic Pope]

If you want more of Hornet squadron and Robinson's black humor mixed with rather graphic combat, Then I can recomend the sequel "A good clean Fight" where they are now in the sahara desert, flying Tomahawks. Unlike Piece of cake, you also hear the story from the Luftwaffe and Afrika Korps point of view, aswell as the SAS patrol that they are hunting.
I've only read those two of his. I keep meaning to read Robinson's WWI books but can never decide what order to read them in (There are 2 prequels to his first book "Goshawk Squadron").

For another WWII fiction you can't get much better than Len Deighton's "Bomber". An epic story about Lancaster crews, German night fighters, and inocent German civilians in a night of hell.

If you prefer some non-fictional epicness (haha even says epic on the cover) then "Vulcan 607" by Rowland White is where its at. Its about the first retaliation strike against the Argentines in the Falklands war, and how in hell do you get an almost retired high altitude bomber designed in the 1940's, to the other side of the planet to do a low level attack on an airfield while avoiding modern SAMs, when the aircraft has no in flight refueling capability and the crew has no training in those areas. Then add a very stormy night to the unbeleiveableness. Its a must read.

I've got a few more that I'll post later.