David Michaelis first contacted the family of Charles M. Schulz seven years ago about writing a biography of Schulz, the creator of the “Peanuts” comic strip. It turned out that Schulz had read Mr. Michaelis’s biography of N. C. Wyeth, and that Schulz’s son Monte also liked the writer’s work. He ended up helping persuade the rest of the Schulz clan to cooperate with Mr. Michaelis, granted full access to his father’s papers and put aside his own novel writing to help him.

But Monte Schulz said that when he read Mr. Michaelis’s manuscript in December, members of the family were shocked by the portrayal of a depressed, cold and bitter man who was constantly going after different women.

“It’s not true,” Monte said. “It’s preposterous.”