3rd and most bonkers mystery in the Cormorant Shrike series by Robbie Galbraith. The 1st two mysteries were much more straightforward; Cuckoo's Calling was about a murder (cunningly disguised) for the purposes of getting an inheritance, the Silkworm was a murder for revenge & publicity. Career of Evil had multiple bizarrely sexual murders by an insane serial killer mastermind whose head we get into, & who's got it in for Strike, and who also likes Blue Oyster Cult. Strangely, I found Career of Evil the mystery I had the best chance at figuring out before the end; I still didn't, but I felt I could have, and that's probably deliberate. The clues were all out there for me to figure out, if only I had been able to see past all the red herrings! I would class Career of Evil as a variant of the Locked Room Mystery, the "Locked Memory Palace Mystery", in that instead of all the suspects being locked in a well-appointed room with the detective, they are all from somewhere in the Detective's past. I was pleased that the Blue Oyster Cult references were not limited to BOC's classic 70s albums (e.g. Agents of Fortune), but also included references to their 1980s "Album-Oriented-Rock" phase (see Club Ninja), and to Heaven Forbid, their final album of the 90s.