"Artillery Flyers at War - A History of the 664, 665 and 666 'Air Observation Post' Squadrons of the Royal Canadian Air Force" by Darrell Knight, has just been released from Merriam Press in Bennington, Vermont, USA. Book is available in hard-cover with jacket, and soft cover.
The book (483 pages) provides excellent detail of the history of the Canadian Auster squadrons raised in England and sent into battle near the end of World War Two (in Europe).
Apparently, Knight was also a minor contributor to another excellent history of the Canadian Auster squadrons, published by Lt.-Col. Dave Fromow and the Canadian AOP Pilots Association under the title "Canada's Flying Gunners" (2002).
I have read both books, and in tandem they provide a lot of information on the training of AOP pilots and observers, the Auster V and the manner in which British and/or Canadian squadrons engaged their enemy in the North African-Italian-European campaigns.