THIS EXCEEDINGLY long novel is so packed with good intentions that it practically begs to be liked, but this hope is defeated by the ineptitude of the book's construction. James Carroll is clearly a writer of deep convictions on any number of important matters; in Prince of Peace, though, he has not found a satisfactory way to translate those convictions into interesting fiction. Instead he has written a gassy, didactic novel that only intermittently engages the reader's emotions and from the outset strains the reader's credulity past the snapping point.

The narrator of the novel is Frank Durkin, a New Yorker who has joined an English Benedictine monastery and is now at a "contemplative outpost" in Israel. Though Durkin is occasionally a participant in what takes place, Prince of Peace is not his story but that of Michael Maguire, who "was the most famous priest in America for a time; the priest against Vietnam" and until a few years ago was Durkin's closest friend. The novel describes, in the most elaborate detail, Maguire's most private thoughts, emotions and actions during periods when he and Durkin were thousands of miles apart. The reader apparently is expected to believe that Durkin is privy to all this information; but the reader, being no fool, does not.

Thus Prince of Peace seesaws erratically between the occasional plausible periods when Durkin is witness to and/or participant in the action, and the far more frequent implausible ones when he simply disappears, unannounced, into the mask of omniscient author. The effect, for even the most tolerant reader, is jarring; just when you've been lulled into forgetting that Durkin exists, suddenly he pops back into the narrative to offer a ponderous aside, of which the novel has all too many, or to resume his own role in the proceedings.

This role, such as it is, is that of the betrayed. Within only a few pages we learn that a decade ago Durkin, then a university professor, had lost his wife to the defrocked priest Maguire, with whom she had been having an affair for years. Now his young daughter, Molly, has come to Jerusalem to tell him that Maguire is dead at 50 of a heart attack and to entreat him, at her mother's request, to come back to New York for the funeral. His bitterness is still great but he agrees to do so, out of respect for the past they shared and out of lingering love for both Maguire and Carolyn, the woman they both married.

HIS JOURNEY to the funeral becomes, of course, a journey into the past. The story begins in Inwood, a small working-class neighborhood at the northernmost tip of Manhattan, where Maguire and Durkin grew up under the rigorous discipline of the neighborhood priests. From there Durkin goes to New York University and Greenwich Village, where he learns skepticism, and Maguire goes to Korea, where he commits an act of heroism that results in his capture by the Chinese. After three years as a prisoner of war, much of that time spent in solitary confinement, he emerges with a powerful commitment to the faith that helped him survive the camp. When he and Durkin meet again in New York, his friend recognizes that he is a rare man:

"I knew already that Michael was not going to be like the rest of us, accommodators, arrangers, moral amnesiacs. His conscience was no leprechaun on his shoulder or prick at the base of his spine; no fog of guilt rolling in after drink or sex or a particularly snide crack about the Jews. Conscience defined his capacity for grappling directly with life itself, including but not limited to what was flawed about it. Saint Thomas says that we are drawn instinctively toward the Good, like plants to light, and it was that trait, more than a dark moralism, though he had streaks of that too, that set Michael apart. At a certain point, later in his life for a brief moment, he became the compass rose for America herself because he could make the right thing known as the only thing."

His passage to that point occupies the bulk -- and bulk, alas, is the word for it -- of the novel. Maguire decides to join the priesthood, attends Catholic University (characteristically, Durkin pauses in mid-narrative to provide an extensive history of that institution, complete with theological commentary), serves his apprenticeship at a New York parish and finally is ordained by Cardinal Spellman, who eventually becomes a considerable figure in the novel. He is posted to a relief operation in Vietnam, where his initial enthusiasm for "what Kennedy called a 'massive joint effort' to help democracy grow out of the ashes of conflict between colonialism and communism" slowly fades as he realizes that the Catholic church of which he is an emissary is condoning the minority Catholic government's repression of the Buddhist majority. It takes several years and a second tour of duty in Vietnam, but in the end Maguire becomes an antiwar activist in the Berrigan mold, and his life takes various dramatic, or melodramatic, turns.

What we seem to have in the life of Michael Maguire is a metaphor for the history of postwar American Catholicism. When he enters the church it is under the inflexible hand of Spellman, who represents both the church's commitment to rigid theological orthodoxy and its longing to establish itself in the American secular firmament. But when the church attempts to silence his protests against the war, he realizes that he is expected to cut his conscience to fit its design; his rebellion against church authority mirrors that of the priests and laymen who, in the '60s and '70s, sought to get out from under the iron hand of Rome and exercise a degree of independence.

The metaphor is all well and good, but it is not enough to sustain a novel that staggers along under the burdens of an unconvincing narrative device, a hackneyed plot and a paucity of genuinely interesting characters. James Carroll is an intelligent writer who is capable of expressing himself with considerable passion, but in Prince of Peace he simply has not given the reader much to care about. Strong feelings aren't enough; fiction also needs real people.