Gosh, this one was hard--I was tempted by a ton of puntastic titles. Runners-up included Sorcery and Cecelia: Or the Enchanted Chocolate Pot, the doubly-puntastic Monstrous Regiment, the groanworthy Sir Apropos of Nothing, and the marvellously understated The Unpleasantness at the Bellona Club. If I hadn't just written a review of it, We Are All Completely Fine would have been in the running as well. Dirk Gently's Holistic Detective Agency is one of the many books on my to-read list solely because of the title. (Speaking of which, how did no-one on my feed choose Hitchhiker's Guide or Goodbye and Thanks for all the Fish?)
But for my final choice, I decided to go pun-free with The Dirty Streets of Heaven, which has to be the most wonderful title ever conceived for an angel-centric hardboiled/noir urban fantasy novel.
Sadly, for me at least, the book didn't quite live up to its title. Maybe that disparity is why it sticks out from the ranks of great titles.