Showing High Midnight by Stuart M. Kaminsky

Someone wants Gary Cooper to make a movie he isn't interested in making, and whoever it is wants him badly enough to get nasty about it. Cooper takes to the hills, accompanied by a writer named Ernest Hemingway, chased by men with blood in their eyes and murder in their hearts. The problem is that Cooper can't shoot straight and Hemingway can't operate without native bearers and an elephant gun.

Toby Peters can't shoot either, but he doesn't need help, much. Just give him a bowl of cereal and time to decide his next move and Toby will get everything straightened out. Now, if he can only keep Lombardi the gangster from making good on his threat to turn him into kosher hot dogs.