At the risk of sounding nerdy, I am currently reading the continuation books of 'Bulldog Drummond' written by Gerard Fairlie following after the original author, H.C. McNeile (Sapper).
The books predate the eventual darker 'Hardboiled' detective genre of the post-WW2 US (which I also enjoy) with British humour, larrikinism and mateship and all those other good things to come out of WWI. There's action, crime, mystery, suspense and everything that makes a good book to me.
At the moment I'm half way through 'Bulldog Drummond on Dartmoor', which was published in 1938