Charles Schulz drew the Peanuts comic strip for almost 50 years, telling 17,897 little stories and watching Charlie Brown, Snoopy, Lucy and the gang grow into an international phenomenon.

He grew rich and famous before his death in 2000. He had every right to be a happy man.

But as the fascinating, exhaustive “Schulz and Peanuts: A Biography” (HarperCollins, $34.95) shows, his personal life was far more complicated than the two-dimensional stories he sketched with such clean lines. And David Michaelis not only tells this story, from Schulz’s boyhood in St. Paul, Minn., to his final years in California, but also shows how it sometimes spilled into the Peanuts story line.

We find, for example, that Lucy sometimes stood in for Schulz’s assertive first wife, from whom Schulz kept an emotional distance just as Schroeder used his piano-playing to keep Lucy away. And we learn that a love-struck Snoopy in 1970 was reflecting Schulz’s extramarital affair.

“All his life he felt alone, spending most of his adult half-century yearning to be taken care of, to be understood,” Michaelis writes. “He would struggle to love and be loved.”

That loneliness was useful; he drew on it to make Peanuts a success. He also figured that what he called his melancholy, or anxiety, was handy for his profession. But his loved ones paid a price. His first wife divorced him. His second wife concluded that in their marriage, “it was important that I not be needy.”

Michaelis vividly sketches the trajectory of Schulz’s personal life and professional career, portraying an ambitious man who always harbored doubts about how far he had come from being “a nothing young man,” even as he became a giant among cartoonists.

By chance, Schulz died just hours before his farewell Peanuts strip appeared in Sunday newspapers. Michaelis finds that fitting.

“To the very end, his life had been inseparable from his art,” Michaelis writes. “In the moment of ceasing to be a cartoonist, he ceased to be.”