San Diego.

Dreaming with His Eyes Open: A Life of Diego Rivera, by Patrick Marnham (Knopf, 350 pp., $35)

Diego Rivera: A Retrospective, by Linda Downs (Norton, 372 pp., $85)

The workmen started swinging their axes at midnight. Within a few hours, they had demolished Diego Rivera's mural in the lobby of the RCA Building at Rockefeller Center, initiating one of the most notorious scandals in the history of American art.

Less than a year earlier, in 1933, Rivera had come to New York City at the suggestion of Nelson Rockefeller. But his work-in-progress had departed significantly from the agreed-upon design; Rivera, a Communist, had infused it with images depicting capitalism as evil and Marxism as society's salvation. When managers inspecting the site spotted a picture of Lenin, they ordered the artist to halt. For months the mural remained unfinished, the center of controversy. A last-minute effort to have it dismantled and shipped to the Museum of Modern Art collapsed. Finally, it was destroyed.

As Patrick Marnham reminds us in this intriguing biography, if Rivera had managed to prevent his politics from subsuming his art, he might have gone on to decorate dozens of important buildings in the United States. Shortly before the Rockefeller fiasco, he had completed murals at the Pacific Stock Exchange in San Francisco and in the Garden Court at the Detroit Institute of Arts. After it, a deal for a mural at the General Motors Building in Chicago was abruptly cancelled. Rivera retreated to his native Mexico, where he had established his reputation as the world's foremost muralist.

Rivera was born in 1886, the product of Mexico's mestizo melting pot; his ancestors made him part Spanish, Indian, African, Italian, Jewish, Russian, and Portuguese. He showed an early aptitude for drawing. At age nine, writes Marnham, "he executed a pencil sketch of his mother that was so unflatteringly accurate that she told him never to draw her again."

After a frustrating stint in Europe, Rivera returned to Mexico in 1920 and found his muse among the people of his native land. Stylistically, he combined Italian-Renaissance frescoing, pre-Colombian images, and Cubist spacing to create a distinctly Mexican aesthetic. His subjects were at times glaringly political, but his finest works overcame this tendency, celebrating the ordinary lives of everyday people. Marnham describes this well, but his book contains only a few dozen examples of Rivera's work. A better source is Linda Downs's newly reissued Diego Rivera: A Retrospective, which includes two hundred color plates.

Marnham does provide a fascinating description of the challenges Rivera faced in producing his grand murals. The artist had to work with certainty and speed, painting over damp coats of plaster as they dried, knowing that colors would fade overnight yet having to match them to the previous day's work. Owing to chemical reaction, the colors themselves fused to the wall. A mistake required cutting away a section of the wall and starting over.

Rivera was well suited to this demanding medium, producing works at once physically awesome and intellectually engaging. "If medieval art was the Bible of the Illiterate, Rivera's frescoes are the Kapital of the Illiterate," wrote one critic. Unfortunately, Marnham fails to explain his subject's contradictory relationship with Com- munism. Rivera never read deeply into Marx or Lenin, nor did he refuse commissions from leading American industrialists.

One such commission led to the Detroit project, widely regarded as his masterpiece, which portrays a Ford assembly line. His two principal murals there, each 800 square feet, are glorious representations of human and mechanical energies converging in production-a Depression-era homage to America's work ethic and economic power. One panel managed to spark outrage from religious leaders for apparently showing the Christ child receiving a vaccination.

What sort of man was Rivera? The first thing people noticed about him, writes Marnham, was neither his art nor his ideology but his sheer size. He sometimes weighed as much as 300 pounds. He also rarely bathed. "Is this the great Diego Rivera?" asked Lupe Marin at their first meeting. "He looks horrible to me." Even so, she later married Rivera-one of five women who did. Marriage meant little to the artist. Rivera was a true lecher, and he twice abandoned wives who had just given birth to his children.

With Rivera, sex frequently intersected with politics. Not long after returning to Mexico, he joined the Trotskyite International Communist League. When Trotsky himself faced expulsion from Norway in 1936, Rivera petitioned Mexican president Lazaro Cardenas to grant asylum to the one-time Russian revolutionary. In early 1937, Trotsky and his wife arrived in Veracruz. Soon they were living under Rivera's roof. Trotsky knew Stalin wanted him dead, but he remained safe as long as he stayed with Rivera. The guest, however, betrayed his host. He made the fatal mistake of having an affair with Rivera's wife at the time, Frida Kahlo-an artist vastly overrated today by feminist advocates. While Rivera had tolerated some of Kahlo's previous flings, especially when they involved women, he became incensed at this one and ejected Trotsky from his home. In 1940, a Soviet agent in Mexico killed Trotsky with an ice pick.

By then Rivera's greatest accomplishments were behind him. In 1957, he suffered a stroke that left him unable to use his right arm. Rivera continued to paint, but two months later succumbed permanently when his heart failed. Before Marnham's biography and the Linda Downs retrospective, there were few reliable sources about Rivera in print. Their publication will guarantee his continuing-and deserved-popularity.