One of Us Is Wrong — Donald E. Westlake

Actor Sam Holt has packed in Packard, the TV detective he played for several years to much acclaim and lots of money. But success has had its downside: Holt is so closely identified with Packard that he can't get hired to play anyone else. Suddenly, though, someone seems to have a new role for Holt: the role of Dead Body. Years of having watched stunt-drivers do their stuff help Holt avoid becoming a grease-spot on the San Diego Freeway, but his Volvo will never play the violin again. And if Holt can't figure out where the screenwriters are going with this one, he's not going to get a chance for a second take.