#RetroHugos1941 The Last Man (aka No Other Man) by Alfred Noyes
I know, I thought I'd wrapped up my Retro Hugo reading, but then over on File 770, Kyra alerted me to this interesting novel, in which almost all of humanity is destroyed by a Doomsday Weapon at the very beginning, the hero spends many chapters exploring dead cities and finding the heroine, and they must then deal with the villain (the hero's surname is Adams; the heroine's first name is Evelyn). It's pretty heavily steeped in the writer's Catholicism and hostility to war; there is a lot of poetry (including some very coy use of Theocritus in the original Greek when the central relationship is consummated); the twist at the end appears to be a case of direct divine intervention. But it's nicely done, and it knocks Jack Williamson off my nominations list.
The author is best known for his ballad The Highwayman, first published many years earlier in 1906.