Robert Mason wrote a follow up book about his experiences after Vietnam, can't find my copy nor does it appear on Amazon. He also wrote some novels, "Weapon" being one.
[Edited to add this ] I found his follow on book on
ABE - it's called "ChickenHawk - Back in the World - Life After Vietnam.
As for other aviation books, I've got one about Australian helicopter pilots in Vietnam called "Get the Bloody Job Done" ( Steve Eather, pub. Allen and Unwin, ISBN 1-86448-802-6 ).
And in the US, most large bookstores have a reasonable selection of first and second-hand accounts of helicopter in Vietnam books - "Low Level Hell" and "Let a Soldier Die" are two that spring to mind.
[This message has been edited by The Nr Fairy (edited 30 June 2001).]