If any writer would have benefitted from a word processor it would have been Proust, whose entire method consisted of adding details here and there,"" guesses novelist White (The Farewell Symphony, 1997, etc.) in his knowing, conversational brief life of the ""valedictorian of the Belle Epoque."" An early draft of Swarm's Way, as White reports, was rejected by a French publishing house with the comment: ""After 712 pages of this manuscript . . . one has no notion, no notion at all of what it's all about. . . . . What does all this mean? Where is it all leading?"" White ably reviews the familiar contours of Proust's (1871-1922) socially gadabout yet also notoriously reclusive adulthood, including his romantic, spendthrift infatuations with younger men, his asthmatic invalidism, and his obsessive literary labors. He also provides basic social and historical background, such as the fact that in the Paris of Proust's boyhood, ""At receptions there was inevitably one valet for every three guests--and the valets had to be at least five feet ten inches tall."" This opening entry in the new Penguin Lives biography series, under general editor James Atlas, acquaints newcomers quickly with the novelist; those who already know Proust's work well may prefer a full-length biography. Issued with White's volume is Larry McMurtry's biography of Crazy Horse ($19.95; Jan.; 160 pp.; ISBN 0-670-88234-8).