Noisy, brassy, fringed with sentiment and dollops of bluff field-hockey slang (""How ya doin', kid?""), this is the Chicago-area saga of 19-year-old Sister Kevin Mary's calamitous first year at a teaching mission in the late 1950s--when habits (both of black serge and otherwise) were rigidly prescribed. Having recently emerged, trembling with idealism, from the ascetic training in her order's Mother House, Kevin Mary is hardly prepared for what greets her when she goes to serve among a group of 15 rather worldly teaching sisters: a Superior who uses Shalimar perfume and joshes with a sleek Monsignor (he rushes Mass for golf and passes out 7-Up & Seagram's); meals of huge, juicy hamburgers and Coke (Kevin Mary's weight will rise from 112 to nearly 150); a sister who whips off her corset for auto-travel comfort; or the cancellation of evening prayers because ""it's vacation."" So, in addition to the trauma of teaching 56 first-graders with no preparation (""To be concerned about the technicalities merely showed a lack of Faith and Trust""), Sister Kevin Mary's greatest trial is cleaving to her vows among women who are fighting their own battles to reconcile inner silences with the cacophony outside. There'll be some black nights of the soul, then: ""She wasn't a very good nun. Her teaching was mediocre. Prayer was zilch. Life was just one salty ham and doughy cherry pie""--plus some disturbing visions of handsome Father Doyle crowding out the Deity. And, along with the colorful company (a brilliant alcoholic, an aged Titanic survivor, the lively young ones), there's the growing sense of things being not quite right: the Superior, a cool, upwardly mobile exec, airily treads on some lower-rung sisters; the Somebodies gossip and drink away from the Nobodies; one sister is an eternal victim, cruelly humiliated. Finally, however, it is Sister Marie Marcel, a ""free soul"" (she treats Sister K.M. to drinks at a Loop steakhouse), who will open Kevin Mary's eyes to the true compassion of the community . . . through a cheerful martyrdom. True, all this is too superficial to be deeply affecting (or even remotely spiritual), too anguished to play full-out for laughs. But FitzGerald (author of the Jane Byrne bio, Brass) spent 13 years at a convent, and there's a roistering authenticity here--which may even be a bit shocking for Catholics who remember when the parochial paddle was an essential learning tool . . . and when a glimpse of a wisp of nun's hair was an Occasion for Sin.