Just finished "Landfall" by Nevil Shute.
It is about a young RAF pilot flying in Coastal Command near Portsmouth in late 1939 - early 1940, before the Battle of France and the Battle of Britain. He sinks a submarine and is cited by a naval board of inquiry for sinking a British submarine. He transfers to a northern Bomber Command base, flies on a mission dropping propaganda leaflets on German cities, and then transfers to test flying for a dangerous new anti-ship weapon. There is also a romance with a bar girl outside of his social class - he is a professional RAF officer.
The book was reviewed by George Orwell in 1940:
http://www.nevilshute.org/Reviews/landfall3.php
The book itself has very good pacing, lots of action.
I found it particularly interesting because it is a fiction book about the early war, and published at the time (1940), by a person who was both a good writer and highly knowledgeable about the subject (Shute was a senior aeronautical engineer before the war who also worked in weapon development during WW2). Especially interesting in that a major plot element was death from 'friendly fire' (what a disgusting circumlocution); even if the outcome in the book was scooby-doo, I'm surprised that he was allowed to raise the possibility in a book published during the war, especially at a difficult time for Britain.
A few oddities in this book for the modern reader, which really do bring home the time it was written in , for example, whenever Shute refers to a plane in the book, it is described as a monoplane. Likewise, the discussions about social class.