I once watched a TV documentary about helicopter ops in Vietnam and one of the interviewees was Bob Mason.
He comes across as a thoughtful, insightful guy. I always recommend "Chickenhawk" to anyone with even the slightest interest in rotary wing aviation or indeed the Vietnam war.
Chickenhawk: Robert Mason: Amazon.co.uk: Books
There is a sequel apparently, called (I believe) "Chickenhawk - Back in the World". All about his experiences post-Vietnam. Amazon list it, but it seems quite elusive.
Chickenhawk: Back in the World : Life After Vietnam: Amazon.co.uk: Robert Mason: Books