I've read all of them GTO.
Goshawk Squadron, War Story and Hornet's Sting are set in WW1 focussing on one squadron of the Royal Flying Corps. They look at different characters mainly, although one chap does feature in two books - starting as a green, arrogant, obnoxious recruit and becoming a cynical, war-weary veteran on the verge of flaking out. Very bleak, but with the same dark humour - brings home how bloody the fight in air above the trenches was. Ever see the Blackadder sketch about the '20 minuters'? That joke takes on a more serious edge after reading the books. Many new pilots never had chance to unpack their gear - they were going through them at a terrific rate. Highly recommended.
A Good Clean Fight continues Piece of Cake in part - some of the original characters are now in Africa flying P-40s War-hawks and Kittyhawks for the RAF's Desert Air Force. The other half of the story focusses on an SAS patrol doing hit and run raids on German installations. It's not his best book but still worth a read.
Damned Good Show is the only one I haven't read - it revolves around RAF Bomber Command's early days when it got a pasting before the night attacks of the Strategic Bombing campaign got into full swing.
