JOHN GREGORY DUNNE's new novel has its roots in John O'Hara's Appointment in Samarra, George V. Higgins' Kennedy for the Defense, James T. Farrell's Studs Lonigan, James Joyce's Ulysses, and any number of Ross Macdonald's "Lew Archer" mystery novels. For all that, Dutch Shea, Jr. is an original: a very serious, very funny, very Irish-Catholic, very suspenseful and--when all is said and done--altogether marvelous book.

Outlining its complicated plot is like trying to describe a spiral staircase without using one's hands. Dutch Shea, Jr. is a criminal lawyer. (A black burglar who breaks into his apartment calls him "some kind of pimp lawyer.") As such, his clients include a man who operates an out-call massage parlor, a woman who has run over her own granddaughter with a power mower, a sociopath accused of arson-murder, an inept wheelman who drives away from a robbery with an identifying bumper-sticker on his car, a senile woman confined to a nursing home, and whichever other flotsam and jetsam of society float his way. In the course of earning his sleazy daily bread, he also encounters a slew of judges, policemen, hookers, other lawyers, and assorted characters both criminal and non-criminal who inhabit a city that is a composite of Boston and Los Angeles. As if his professional life is not complicated enough, he is sleeping every so often with a lady judge who was a virgin till she was 31, and whose father still thinks she's one.

It is the blurring of Shea's professional and personal lives, however, that provides the book with its impact and its weight. Three decades ago, Shea's lawyer-father was sent to prison for embezzlement, and subsequently hanged himself in his cell. Young Shea was raised by his father's closest friend, a widower with two children. The daughter has since grown up to be a nun who leaped over the wall. The son is a priest who has achieved celebrity, Ma la Julia Child, as a television cook. Shea is still in close contact with this "family" and also with Lee, the adulterous wife he divorced. Whenever he phones her, it is to argue about their 18-year-old daughter who was blown to bits by an IRA bomb in a London restaurant--while Lee was unforgivably in the ladies room.

Shea is a man who wakes and feels "the fell of dark, not day," a haunted individual clearly at the end of his tether, lonely and desperate and doomed. When his surrogate father gives him a gun after the burglary, we know it will only be a matter of time before he uses it on himself. Why, then, should we bother reading further? Because we hope against hope that Dunne's bright, witty, sad and entirely sympathetic hero will not do what we dread he might do, and because the novel is so rich in character and detail that we are compelled to turn the pages as rapidly as our fingers can move. At one point, Shea thinks, "My life is a Chinese box full of uninvestigated mysteries." Most of these mysteries are skillfully resolved by Dunne in a style that successfully blends interior monologue with ongoing action, briskly and humorously moving the multi-layered plot forward while simultaneously chronicling Shea's gradual disintegration.

The accidental disinterment of his long-dead father, for example, serves a triple-pronged purpose: we are symbolically reminded of the resurrection of Christ; we are advised that the past is always with us; and we are clued to the fact that history is about to repeat itself. The wake of an Irish fireman, as another example, is perhaps the best such evocation I've ever read, but here again, it serves at the same time to bring Shea close to losing complete control. Similarly, the intrusion of the black burglar graphically sums up the shabby condition of Shea's present existence and--because a gun figures largely in the scene-- foreshadows his self-destruction. (As a supremely ironic footnote, Shea is later given the opportunity to defend the very man who threatened his life; to his eternal credit, he does so ethically and nobly.)

Dunne falters only once in his unraveling of the various mysteries in Shea's life, and unfortunately with the single most important plot thread. I am not giving anything away when I mention the name "Kathleen Donnelly" or when I say that although I scrupulously back-tracked her alleged indiscretion through the tangled undergrowth of the past, I was not entirely convinced by Shea's conclusions. I was troubled, too, by some of Dunne's stylistic tricks: the repetition of key words, phrases, or sentences that blink on and off throughout like neon signs outside an all-night L.A. supermarket; the use of brand names to delineate character; the sometimes "Who's-On-First?" exchanges of comic dialogue; the transfer of verbal tics from one character to another, so that some of the people seem interchangeable.

These are minor flaws. Dunne has written a fine novel that examines and dissects a unique individual whom we come to know--and indeed love and admire--as the story unfolds toward its tragic end. By so movingly bringing to life this troubled and complicated man, he has illuminated our own human condition--and that, in the long run, is what good fiction is all about.