C Is For Corpse by Sue Grafton

"My name is Kinsey Millhone. I'm a licensed private investigator... thirty-two, twice divorced. I like being alone and I suspect that my independence suits me better than it should..."

Kinsey met Bobby Callahan in the gym on Monday morning. His story was hard to credit: a murderous assault by a tailgating car on a lonely rural road, a roadside smash into a canyon 400 feet below, his Porsche a ruin, his best friend dead, and his memory severely impaired. He was convinced someone was trying to kill him. By Thursday, he was dead. But Kinsey wasn't going back on a deal. She had been hired to prevent a murder. Now she was looking for the murderer...