Funnily enough, I am currently re-reading Biggles Fails to Return, which was published in 1943 and is set in WWII (I find such books, especially episodes in fictional series - the Chalet School has a similar volume - fascinating, especially given that the authors would have no idea what might happen by the time they were published). Biggles has still failed to show up, a hundred or so pages in, but I am enjoying the tension of everyone looking for him, and the setting, Monaco, is nicely drawn.