The Cuckoo's Calling by Robert Galbraith

After losing his leg to a land mine in Afghanistan, Cormoran Strike is barely scraping by as a private investigator. Then John Bristow walks through his door with an amazing story: His sister, the legendary supermodel Lula Landry, famously fell to her death a few months earlier. The police ruled it a suicide, but John refuses to believe that. The case plunges Strike into the world of multimillionaire beauties, rock-star boyfriends, and desperate designers, and it introduces him to every variety of pleasure, enticement, seduction, and delusion known to man.