This is a little different than I usually read, but why limit myself, right? It's sort of remiiscent of Sherlock Holmes, but the eccentric detective has a past. It's very cleverly done. Told from the point of view of his new assistant, a down and out Welshman who was about to do himself in if he didn't succeed in this last job application. As it happens it was his very desperation that got him the job.
It's a slightly atypical Murder Mystery story, but I didn't guess the culprit before s/he was revealed. What's different about it is the excursion into exotic corners of London subculture, including the Jewish and Asian communities.
I thought it was very well done and the author seems to know his history. Enjoyable for a diversionary read.