The first 20 pages or so of Jincy Willett's mischievously titled novel are so entertaining they nearly wear you out. Those first pages are dense with observations about Rhode Island, where the book takes place, and its inhabitants. (''We have no stage presence at all,'' the narrator explains, ''no Southern theatrics, Midwestern irony, Western hyperbole, New York cynicism.'') And one page consists of nothing but howlingly funny jacket blurbs for a trashy true-crime book about a woman who has killed her abusive husband. (''Abby Mather's triumph is our triumph,'' asserts Victoria Fracas, author of ''Rape, Rape, Rape.'')

Sure, it's all very amusing, but it also sets off the warning bells: is Willett's first novel (she previously published a book of short stories, ''Jenny and the Jaws of Life'') going to be a self-congratulatory stunt, a case of a writer's scrabbling away on the hamster wheel of her own cleverness?

The miraculous surprise of ''Winner of the National Book Award'' is that the answer, free of Midwestern irony or any other kind, is no. The book's narrator is Dorcas Mather, an unmarried librarian and self-proclaimed loner (she's in her mid-40's when the book opens in 1983). Dorcas has a twin sister, Abigail, who's her polar opposite: Dorcas is tall and narrow, and her sexuality and her sensuality find their outlet almost exclusively in the act of reading. Abigail, on the other hand, is large and fleshy and takes her pleasure wherever she can find it. At 14, she lost her virginity to her small-town high school's football team. Years later, the men who were once on that team acknowledge the act, remorsefully, as rape, but Abigail doesn't see it that way. Her view of the event seems woefully delusional, but Willett allows her to have it, perhaps as a way of acknowledging that as much as we'd like to choose tidy, politically correct feelings for characters, the choice isn't ours to make.

But Abigail is emotionally fragile, and both she and Dorcas fall prey, in different ways, to the unmitigated nastiness of Conrad Lowe, a writer, misogynist and former gynecologist who suddenly appears in their town. What happens among the three of them, told here in flashback, makes for a plot that's merely serviceable. Yet, page by page, this novel is effortlessly enjoyable: Willett observes details unsparingly and with great good humor, not to mention refreshingly pointed crankiness. Although Dorcas is in some ways heartbreakingly open to the world around her, she also greets it with exceptionally sharp skepticism. As a librarian (and an avid, loving reader), she reserves her hottest poker for the type of ''worthy'' books that get glowing reviews and then languish, unread and unremembered, on library shelves until someone finally has the good sense to chuck them: ''How well do you remember that, say, six-year-old 600-pager The Times assured you was destined to become a classic? You know. The 'monumental work of fiction' that you were supposed to run, not walk, to the nearest bookstore to purchase, the book that was going to change your life. . . . Winner of the National Book Award. You remember. 'Handleman's Jest.' 'Parameters & Palimpsests.' 'The Holocaust Imbroglio.' We sell these babies for 50 cents apiece, or try to, seven years after they come out. We sell them because no one has checked them out for four years.''

I picture readers around the world -- the people who have more than once been suckered by a good book review -- cackling mercilessly at that passage. And I picture writers around the world -- the people who have written the actual books -- saying ''Ouch.'' And I'm grateful that Willett is willing to crack such a joke at all. It's a joke made for the benefit of readers, not writers or critics. And whom, after all, are books written for? Willett is that rare novelist who writes in the moment -- a glorious place to be -- and not with one eye fixed on the posterity gauge. She writes for the joy of reading, not for the puffed-up pride of having written, and we're the ones who run off with the prize.