Read (Colin) Bateman's Mystery Man, which started off feeling like "Bernard Black as a Private Eye" - but evolved once it became clear that the mystery man is a depressive, aspie, unreliable narrator with lots of other conditions. In fact he has so many conditions (basically, *everything* from allergies to a pacemaker) that it might almost be too much to believe - if not for the fact that I know several people who really are like that!
Anyway, it was great, very touching, clever, funny, didn't handle the POV character's conditions too badly, and there are sequels to look forward to!