The Black Ice by Michael Connelly
When a body is found in a hotel room, reporters are soon all over the case: it appears to be a missing LAPD narcotics detective, apparently gone to the bad. The rumours were that he had been selling a new drug called Black Ice that had been infiltrating Los Angeles from the Mexican cartel.
The LAPD are quick to declare the death a suicide, but Harry Bosch is not so sure. There are odd mysteries and unexplained details from the crime scene which just don't add up. Fighting an attraction to the detective's widow, Bosch starts his own maverick investigation, which soon leads him over the borders and into a dangerous world of shifting identities, police politics and deadly corruption . . .