IT SHOULD be no insult to say that Mass resides in that dark borderland between thriller and novel. This territory is, after all, a rather rich one. In it, you'll also find the best books of George Higgins and Elmore Leonard. Martin Cruz Smith's Gorky Park is there, as are many of Ross Thomas' and all of John Le Carre's except The Naive and Sentimental Lover (in which the English spymaster felt moved to prove he could produce the sort of languid novel that Dirk Bogarde now writes).

If Jack Fuller has a master among these border-lords, then surely it is Graham Greene. Even the title of this Book, Mass, although it puns in the direction of nuclear physics, suggests that Catholic ethics, rather, will be its chief concern. And to underline this, Fuller contributes quotations from Benjamin Britten's War Requiem, lines of the Latin Mass and Wilfrid Owen's war poems to open each chapter. The implications of this are a bit too grand: he promises more than he delivers. While Graham Greene might have been justified in using such a device in Brighton Rock and some others, it doesn't seem to fit the material here.

But what Fuller shares most plainly with Greene is the burden of guilt carried by his characters. Nearly all of them seem afflicted. Stan Majors (n,e Majewski), the crack reporter who investigates the assassination of a defected Russian dignitary, is estranged from his son, David -- and blames himself. Moll, the FBI special agent who is working on the case, is estranged from his son, Tom -- and blames himself. And the man known as Jenkins, who almost certainly has something to do with the bombing, is impelled to act at least partly to attone for a mysterious past sin. All are to some degree burnt-out cases. There is even a priest on hand (as there often is in Greene's novels) to expatiate upon the ways of sin and guilt in his discussions with Majewski.

The Russian defector who has been assassinated is no less than Viktor Shevstov, the father of the Soviet atomic bomb. Somewhat after the fact, he saw the light and started agitating that his creation never be used. Finding the climate in Russia cool to such protest, he made his way to the West. He is on a lecture tour, speaking out in favor of nuclear disarmament when, on the way to a speaking engagement, the car in which he is traveling is blown to bits by an explosive device wrapped in radioactive waste.

The scene is New Haven, and the university at which Shevstov is to speak is Yale, of course -- although, curiously, it is never specifically named. And Fuller is also a bit shy about placing his events in time. Perhaps he means all this to have happened just yesteday -- yet it feels a bit more like the mid- '70s with Vietnam recently past and the long political freeze just setting in.

FULLER, HOWEVER, does manage to be quite convincingly specific about the book's newspaper background (as a reporter, Majewski makes all the right moves) -- not surprising since Fuller is himself a professional journalist, the editorial page director of the Chicago Tribune. But he is just as sure-handed in narrating the FBI investigation from Moll's point of view. (Where did he learn that all such headline cases inevitably devolve into turf fights? Maybe at the Justice Department where he once worked.) And finally, Fuller handles the historical background to the novel -- quite important here -- with great authority, giving the book a resonance and a sense of substantiality that even Graham Greene's often lack.

Predictably enough, the story ends tragically. Yet it is not so much the spectacular events that concern Fuller here as the people who are touched by them. Mass is about real people caught up in violence -- by history, by fate, by professional obligation. The conscientious care lavished by Fuller on his characters is what sets this book apart from the dozen or so thrillers with a nuclear theme that will be published in any given month. This attention to character, clearly, is what distinguishes all such superior novels of the genre from the routine products and places them in that borderland between thriller and novel.

How then is it not simply a novel of violence and its consequences as, say, Conrad's The Secret Agent and Under Western Eyes are? In Mass, Fuller relies a bit too strongly on coincidence and dark secrets from the past to move his story along and provide motivation. But no matter: he has written a good book, one that does the work of a novel and provides what most readers will want in the way of suspense.

With two other such books behind him (Convergence and Fragments), Jack Fuller has demonstrated his power to produce at an impressively high level of performance. If he keeps this up, his will be a considerable name in years to come.