Had some good luck browsing in secondhand bookshops this week ...
Lee Brimmicombe-Wood. The Burning Blue: The Battle of Britain, 1940. Hanford: GMT Games, 2006. NOT a book, a wargame simulating the "plotting table" war, if you like. Product page. Well-researched, as the support page shows. DOES have Boulton-Paul Defiants, does NOT have Gladiators.
Donald Cowie. An Empire Prepared: A Study of the Defence Potentialities of Greater Britain. London: George Allen & Unwin, 1939. Published for the Right Book Club. About how all the red bits on the map will help Britain if war comes. Introduction by Lord Lloyd, former Governor of Bombay and High Commissioner of Egypt.
Harry Golding, ed. The Wonder Book of Aircraft for Boys and Girls. London: Ward, Lock & Co, 1919. Was I as giddy as a schoolboy when I saw this in a bookshop for only $10? You betcha! Lots of illustrations, though unfortunately some have been cut out (no doubt to grace some long-forgotten school project), including eight by Heath Robinson! Clarification: that was badly phrased -- the Heath Robinson pics weren't the ones that were cut out, luckily.
Robert Graves and Allan Hodge. The Long Week-End: A Social History of Great Britain, 1918-1939. London: Four Square Books, 1961 [1939]. A classic work of contemporary history, in a groovy new edition for the new generation.
Richard Jefferies. After London or Wild England. London: Duckworth, 1929 [1885]. Only very tangentially relevant to my areas of interest, mainly as an early example of some catastrophe doing for London and dramatically re-ordering English society.
George Rochester. The Despot of the World. London: John Hamilton, 1936. A thrilling (one assumes) novel of the Soviet menace, air combat over Siberia, and how world war was averted. Part of the "Ace" series of books, along with Biggles and others (indeed, there's a big selection of other aviation titles in the catalogue at the back of the book). My copy was given to one Peter Johnston at Xmas 1936, as the Third Prize "for improvement in Pianoforte".