In Jeffrey Eugenides’s remarkable and absorbing work “The Marriage Plot: A Novel,” the plot is paramount yet sometimes nearly invisible as the reader gets lost in the minds of the three main characters, who are just finishing their college careers at Brown University. Mitchell Grammaticus, Madeleine Hanna, and Leonard Bankhead are heading different directions, and in fact their travels to Cape Cod, Paris and Monaco, and Calcutta receive the full benefit of Mr. Eugenides’s extraordinary novelistic gifts. But it’s the questing that fascinates. Mitchell is after meaning and truth, while Leonard is in the grips of madness. Maddy delays her own independence and the pursuit of her career in order to sojourn with Leonard. The story weaves back and forth, but the reader is barely aware of the high-wire act the author must do in order to keep it together. There are dazzling long sequences with never a wasted word and dead-on dialogue: even the secondary characters’ voices are unique and recognizable. It’s a rare thing to find a novel this high-minded yet gripping, and several of the twists and turns elicit vocalizations: chortling or gasping. (The scene that has Maddy and the manic Leonard checking into their Monaco hotel blends the two.) It continues this way, right down to the revelation on the last page, when the story concludes in the only plausible way, and the three main characters are nobler for the experience.