I HAVE ONLY one problem with David Morrell's taut, tightly written thriller about a community of Roman Catholic monks who serve as assassins "for the good of the Church." The Fraternity and its chief, one Father Stanislaw -- a kind of clerical Rambo -- are far too efficient to be Catholic.

The Roman Catholic Church is the only institution in the world which is exempt from the Peter Principle: in the church you can be promoted far beyond your level of incompetence. To anyone who has had to deal with cardinals, bishops, papal nuncios, college presidents and monsignors, the skill and effectiveness of the Fraternity of the Stone are simply beyond belief. So too, by the way, is the wisdom of the Opus Dei, described not altogether accurately by Morrell as the church's CIA.

Personally I am delighted by the inefficiency of the ecclesiastical institution (and especially of the sinister Opus Dei). It is precisely the inefficiency of the church which leaves so much room for initiative and creativity at the grass roots and, on the natural level, is one of the reasons for Catholicism's durability. If there were a religious order of monk/killers they would be about as good at their business as was the Vatican bank or the people at Notre Dame who choose football coaches.

But if one is willing to suspend belief on this point, Fraternity, like Morrell's earlier novels First Blood and The Brotherhood of the Rose, is a well paced, ingenious, and satisfying adventure yarn. Drew MacLean is recruited by Scalpel, an American anti-terrorist organization, because he wants to avenge the murder of his parents by terrorists when he was a boy. He wearies of the killing, especially when he is responsible for the death of the parents of another 10-year-old. He disappears, apparently "phased out" by Scalpel, and withdraws to a Carthusian monastery in New England to do penance for his sins and save his soul.

One night all the other monks in his monastery are murdered. Trying first to escape and then to seek vengeance, Drew enlists the aid of his sometime lover and her brother. They encounter Stanislaw and his bunch -- a medieval order founded to fight Moslem terror during the crusades with counter terror -- and must decide whether Scalpel or the Fraternity killed the monks and is trying to do Drew in.

Drew must also face the "vocation" -- hardly voluntary -- to join the Fraternity.

At the end, much remains unresolved. Perhaps there will be a Fraternity of the Stone: Part Two, especially since Drew possesses the stone which is the symbol of the Order's leadership.

THE "spy" thriller is acceptable as a genre because one knows that like the mystery and the western, it is a genre and not reality. If all the mayhem described in Fraternity (or any similar story) was thought to be real, it would indeed be a terrifying book. One knows that the stories are fantasy, not unlike Buck Rogers or Flash Gordon or Star Trek or Indiana Jones or James Bond.

Or one did know before Watergate. Since then there has been the unpleasant possibility that fact may model itself on fiction, that reality may be shaped by stories, that there might be a shadow world as bad or even worse than that depicted in the thrillers. That thought kind of spoils the fun for some of us.

Religious order killers? Impossible. Men might lie and steal routinely for the "good of the Church." But not kill. Yet were there not military orders in the middle ages -- Teutonic Knights, Knights Templar, Knights Hospitalers (the current quite harmless Knights of Malta) -- who were willing to fight wars for the good of Christianity? And do not the missionaries who advocate class conflict implicitly and unintentionally (perhaps) seem to suggest violence, not for the Church indeed, but for the "poor"? Do they think no one gets killed in revolutions?

In its best moments, Catholicism does not generate fanatical violence. We are not currently into killing a Shiite for Jesus. In our worst moments, we did just that. In all the religions of history (those which see a world moving towards salvation), the temptation to fanaticism necessarily lurks just beneath the surface. I see no reason to believe that the temptation is any less seductive today than it ever was. Only the forms are different.

As a "good read" The Fraternity of the Stone is enjoyable. As a perhaps unintentional warning to all of us who are heirs of the religions of history, it is a disturbing and profitable challenge to conscience.

Father Andrew M. Greeley, professor at the University of Arizona, is the author of "Virgin and Martyr" and "Happy are the Meek." The Shadow of the Killer Monks THE FRATERNITY OF THE STONE By David Morrell St. Martin's. 375 pp. $16.95 By Andrew M. Greeley

I HAVE ONLY one problem with David Morrell's taut, tightly written thriller about a community of Roman Catholic monks who serve as assassins "for the good of the Church." The Fraternity and its chief, one Father Stanislaw -- a kind of clerical Rambo -- are far too efficient to be Catholic.

The Roman Catholic Church is the only institution in the world which is exempt from the Peter Principle: in the church you can be promoted far beyond your level of incompetence. To anyone who has had to deal with cardinals, bishops, papal nuncios, college presidents and monsignors, the skill and effectiveness of the Fraternity of the Stone are simply beyond belief. So too, by the way, is the wisdom of the Opus Dei, described not altogether accurately by Morrell as the church's CIA.

Personally I am delighted by the inefficiency of the ecclesiastical institution (and especially of the sinister Opus Dei). It is precisely the inefficiency of the church which leaves so much room for initiative and creativity at the grass roots and, on the natural level, is one of the reasons for Catholicism's durability. If there were a religious order of monk/killers they would be about as good at their business as was the Vatican bank or the people at Notre Dame who choose football coaches.

But if one is willing to suspend belief on this point, Fraternity, like Morrell's earlier novels First Blood and The Brotherhood of the Rose, is a well paced, ingenious, and satisfying adventure yarn. Drew MacLean is recruited by Scalpel, an American anti-terrorist organization, because he wants to avenge the murder of his parents by terrorists when he was a boy. He wearies of the killing, especially when he is responsible for the death of the parents of another 10-year-old. He disappears, apparently "phased out" by Scalpel, and withdraws to a Carthusian monastery in New England to do penance for his sins and save his soul.

One night all the other monks in his monastery are murdered. Trying first to escape and then to seek vengeance, Drew enlists the aid of his sometime lover and her brother. They encounter Stanislaw and his bunch -- a medieval order founded to fight Moslem terror during the crusades with counter terror -- and must decide whether Scalpel or the Fraternity killed the monks and is trying to do Drew in.

Drew must also face the "vocation" -- hardly voluntary -- to join the Fraternity.

At the end, much remains unresolved. Perhaps there will be a Fraternity of the Stone: Part Two, especially since Drew possesses the stone which is the symbol of the Order's leadership.

THE "spy" thriller is acceptable as a genre because one knows that like the mystery and the western, it is a genre and not reality. If all the mayhem described in Fraternity (or any similar story) was thought to be real, it would indeed be a terrifying book. One knows that the stories are fantasy, not unlike Buck Rogers or Flash Gordon or Star Trek or Indiana Jones or James Bond.

Or one did know before Watergate. Since then there has been the unpleasant possibility that fact may model itself on fiction, that reality may be shaped by stories, that there might be a shadow world as bad or even worse than that depicted in the thrillers. That thought kind of spoils the fun for some of us.

Religious order killers? Impossible. Men might lie and steal routinely for the "good of the Church." But not kill. Yet were there not military orders in the middle ages -- Teutonic Knights, Knights Templar, Knights Hospitalers (the current quite harmless Knights of Malta) -- who were willing to fight wars for the good of Christianity? And do not the missionaries who advocate class conflict implicitly and unintentionally (perhaps) seem to suggest violence, not for the Church indeed, but for the "poor"? Do they think no one gets killed in revolutions?

In its best moments, Catholicism does not generate fanatical violence. We are not currently into killing a Shiite for Jesus. In our worst moments, we did just that. In all the religions of history (those which see a world moving towards salvation), the temptation to fanaticism necessarily lurks just beneath the surface. I see no reason to believe that the temptation is any less seductive today than it ever was. Only the forms are different.

As a "good read" The Fraternity of the Stone is enjoyable. As a perhaps unintentional warning to all of us who are heirs of the religions of history, it is a disturbing and profitable challenge to conscience.