Author Jonathan Santlofer spent days toiling over a crucial part of his new thriller, "The Killing Art," trying to fit in 58 separate characters, including a wealthy arts patron, a gallery owner, a poet, a psychiatrist and a famous Hollywood actress. He kept adding, deleting and rearranging. Even as his book was being sent to the printer, he begged his editor to make one final change.

Mr. Santlofer's literary challenge: The acknowledgments. "They might be two of the most thought-about pages in the book," he says.

Some of the people on the list were a bit perplexed. Among them was Diane Keaton, thankee No. 46. "I have not contributed anything," says the Academy Award-winning actress, "and I mean zero."