C is for Corpse by Sue Grafton

C IS FOR CALCULATED
How do you go about solving an attempted murder when the victim has lost a good part of his memory? It's one of Kinsey's toughest cases yet, but she never backs down from a challenge. Twenty-three-year-old Bobby Callahan is lucky to be alive after a car forced his Porsche over a bridge and into a canyon. The crash left Bobby with a clouded memory. But he can't shake the feeling it was no random accident and that he's still in danger…

C IS FOR CRIME
The only clues Kinsey has to go on are a little red address book and the name "Blackman." Bobby can't remember who he gave the address book to for safekeeping. And any chances of Bobby regaining his memory are dashed when he's killed in another automobile accident just three days after he hires Kinsey.

C IS FOR CORPSE
As Kinsey digs deeper into her investigation, she discovers Bobby had a secret worth killing for―and unearthing that secret could send Kinsey to her own early death…