On page 265 of Deborah Jowitt's exhaustive, exhausting bio, she writes: ''When you mention the name of Jerome Robbins to people not deeply attuned to dance or theater, an unspoken question sometimes hangs in the air. Then you say, 'West Side Story.' [And] they understand that he was important.'' Jowitt clearly isn't writing for the not deeply attuned, but even committed terpsichoreans may find her book a dry, dutiful trudge through the life of America's most electrifying and infuriating 20th-century choreographer. She drones too often in analysis of Jerome Robbins' aesthetic and treads too delicately in the tabloid rough of his life (his name-naming before HUAC, his affair with Montgomery Clift).