By Scott Turow

Farrar, Straus and Giroux. 515 pp. $22.95

SCOTT TUROW'S second novel proves beyond any reasonable doubt that his hugely successful first was no fluke: If you liked Presumed Innocent -- and millions did -- you're going to love The Burden of Proof. It's that's rare book, a popular novel that is also serious, if not "literary," fiction. The Burden of Proof means to entertain, and does so with immense skill, so if all you want is intelligent amusement it will serve you handily; but it is also a complex, multi-layered meditation on "the heartsore arithmetic of human events," and as such rises far above the norm of what is generally categorized as "commercial" fiction.

In his two novels Turow has demonstrated that there is still life in the old American traditions of realism and naturalism. His linear forebears are not the manufacturers of assembly-line entertainments and romans a` clef but the likes of Theodore Dreiser and James Gould Cozzens: serious but not self-consciously literary writers who (in Dreiser's case at least) were less interested in prose style than in the great clanging engines of American society and in the institutions -- most particularly business and the law -- that operate them. Turow to be sure seems to have his eye more sharply focused on the marketplace than did Dreiser and Cozzens, but he shares their preoccupation with the whole range of American life and their sense of moral urgency.

There is indeed a dark side to Turow's fiction that stands in striking contrast to the elaborate maneuverings of his extremely complicated plots. The Burden of Proof opens with a terrible event -- the suicide of Clara Stern, the wife of its protagonist, Sandy Stern -- and is haunted by that event for the rest of its considerable duration. The story takes us into the labyrinthine worlds of commodities futures trading and of the federal district courts, which is to say that it provides much with which both to amuse and instruct us; but these matters are essentially peripheral -- important but scarcely essential -- to the novel's real business, the exploration of the heart and mind of Sandy Stern.

Readers of Presumed Innocent will recall him: Alejandro Stern, the midwestern lawyer whose defense of Rusty Sabich, the prosecutor wrongfully accused of murdering a colleague, established his reputation. Now, a few years later, he is 56 years old and has come home one day to find himself a widower: " 'What did I do?' he asked repeatedly in a tiny stillborn voice as a rushing storm of grief blew through him. 'Oh, Clara, Clara, what did I do?' " It is this question, this inability to understand his wife's self-inflicted death, that underlies everything Stern thinks and feels and does; it is an obsession that colors every aspect of his life both private and professional.

It is in fact one of the great strengths of The Burden of Proof that it establishes these interconnected lives and explores them so intimately. Unlike our more determinedly literary writers, Turow understands both that work is essential to the shaping of American lives and that a person's work cannot really be separated from his "private" self. No doubt this has much to do with Turow's own successful career in the law, which seems to have taught him not merely the familiar truth that it's hard not to take the office home with you but also the unfamiliar one that it's just as hard not to take home to the office with you.

In Sandy's case this is exacerbated by the realization, which dawns gradually but soon enough acquires a gravity bordering on fixation, that Clara's death was connected in some unknown way with the case on which Sandy is now working. His brother-in-law, Dixon Hartsell, a country boy turned financial wizard, is under investigation by federal authorities for possible abuses of inside knowledge of the commodities market; one by one other Sterns and Hartsells are sucked into the case, until at last it becomes a "bleak morass of family difficulties" from which Sandy -- not to mention the others -- must learn any number of painful if illuminating lessons.

The case has all the ingredients of a big one; it sets the chief federal prosecutor, no friend of Sandy's, to "palpitating at the thought of a case that would get his name in The Wall Street Journal and bring a moment of disquiet to that den of thieves in the Exchange, as he saw them, with their granite palace along the river." Here as in his previous novel Turow is positively brilliant at tracing his various attorneys' motives right down to their mean, competitive essence, yet he retains throughout a realistic appreciation both for lawyers and for the law itself:

"Some spoke of the nobility of the law. Stern did not believe that. Too much of the grubby boneshop, the odor of the abattoir, emanated from every courtroom he had ever entered. It was often a nasty business. But the law, at least, sought to govern misfortune, the slights and injuries of our social existence that were otherwise wholly random. The law's object was to let the seas engulf only those who had been selected for drowning on an orderly basis. In human affairs, reason would never fully triumph; but there was no better cause to champion."

SANDY is above all else a rational man; even in this time of the most intense personal trial he maintains his lawyerly composure, though there are moments when to do so requires a real exertion of the will. "His life as he had known it was gone," he knows, "and the road down which he marched seemed completely beyond him. What was ahead?" He is a middle-aged man at the beginning of a new life -- discovering his grown children for the first time, rediscovering the lost world of women and sexuality and romance, arguing a case that has the potential to destroy his family -- who finds himself both shaken and expectant; surely nothing is more wholly accomplished in this fine novel than its exceptionally subtle, knowing exploration of the myriad ways in which a life can be reborn at any juncture in its course.

So many things are happening in The Burden of Proof that a review can only hint at them. But certainly these should be mentioned: the sharp, perfect dialogue; the slow unfolding of Clara's legacy, which Stern first sees as a list of "gruesome surprises" but eventually understands as something at once kinder and more complex; the relationship between Stern and Dixon, which in Clara's absence becomes the paramount connection in Stern's existence; the evocation, familiar to those who know Presumed Innocent, of the courthouse and those who inhabit it.

The temptation to make too much of The Burden of Proof is great and difficult to resist. Suffice it then to say that it is a big old-fashioned novel of the sort for which readers still seem to thirst, but that it is much more: a work of seriousness and depth that rewards the reader with far more than he'd bargained for.