"PAIN, PARTIES, WORK: SYLVIA PLATH IN NEW YORK, SUMMER 1953." By Elizabeth Winder. Harper. $25.99."I was supposed to be having the time of my life," Sylvia Plath's young protagonist sighs in the 1963 classic "The Bell Jar." Sulking, acerbic Esther Greenwood -- Holden Caulfield in a shantung sheath -- is in Manhattan, supposedly "having a real whirl," but is actually spending most of her time obsessing over executions and stuffing herself with expensive condiments. "I just bumped from my hotel to work and to parties and from parties to my hotel and back to work like a numb trolleybus," she admits. She manages to make New York and all of its youthful splendors sound like a Bataan death march for striving debutantes, which, while not unrealistic, is hardly the Manhattan dream.