Mark Rothko’s so-called “classic style” works, with their hovering rectangles of insubstantial color, are among the best known and most passionately admired of abstract paintings, as easily recognized and readily parodied as Jackson Pollock’s poured tangles and, it seems, far more beloved. But Rothko didn’t paint the first of his “classic style” compositions until late in 1949, when he was forty-six. (Born Marcus Rothkowitz in Dvinsk, Russia, in 1903, he died, a suicide, in New York in 1970.) When he began the series that would preoccupy him for the rest of his life and define him as an artist, he had been painting for a quarter of century and exhibiting for more than twenty years; he began to study with Max Weber at the Art Students League in 1925 and was included in his first New York group show in 1928. The floating rectangles that are now synonymous with Rothko’s name were not the result of a sudden decis ...