O'Neill's brilliant 2002 breakthrough novel, ''At Swim, Two Boys,'' swirled history, politics, and sexuality into a raging Irish tempest. ''Kilbrack,'' written in 1990 and just now published in America, is more of a teacup -- small, warm, and beautifully ornamented -- that portends the eventual flowering of a major talent. It begins as the story of a young amnesiac on his way to an Irish village, the subject of a memoir that's obsessed him. Why amnesia? Why this village? The tragicomic answers make ''Kilbrack'' smarter and more haunting than the novel's minor, mirthful shape suggests.