He rose to prominence as a portraitist in the 1950s, photographing celebrities such as composer Igor Stravinsky, jazz musicians Duke Ellington, Dave Brubeck, and Thelonious Monk, prima ballerina Maria Tallchief, and first lady Eleanor Roosevelt.

[1][2] Brook's photographs were published widely in magazines such as Time, Vogue, Popular Photography,[1] and ARTnews.

[4] In 1966 he was one of 20 photographers whose work was featured in Life magazine's 30th Anniversary Photography Special Issue; others included Richard Avedon, Henri Cartier-Bresson, and Robert Doisneau.

[1] Boston artist Steven Trefonides cited Brook as a formative influence.

His photographs can also be found in two published volumes: A Long the River Run (Scrimshaw Press, 1970) and Hold Me (Aura Publications, 1977).