Flakes, Nuts and Capitalists : THE ROAD TO WELLVILLE, <i> By T. Coraghessan Boyle (Viking: $22.50; 476 pp.)</i>

One of the more endearing and exasperating facets of the American appetite is its hunger for self-improvement. Think of Bill Moyers and his attentive, homespun, secular romanticism; he roams from coast to coast like a political candidate--our candidate--on a eternal campaign for betterness, for a philosophy or paradigm that will lend coherence to our lives on this messy, bloated continent. If the old religions fail to serve us, we invent new ones--or recycle slightly used ones. If nothing else, it keeps us busy.

It keeps our satirists busy, too, ofcourse. And none more prolifically or acutely so than T. Coraghessan Boyle, who thrives on our aspirational mania in all its forms. Since his breakthrough with “World’s End” (1987), Boyle, a prodigiously gifted, high-octane prose writer, has been on something of a creative roll, culminating in his last and funniest novel, “East Is East.” With each new book it becomes harder to resist the confidence and exuberance of his style, the boldness of his reach.

In “The Road to Wellville” (from a slogan of C. W. Post’s), he gives us turn-of-the-century Battle Creek, Mich., with its gold-rush ambience of cereal manufacturers, health food enthusiasts and scam artists, and its god-like presiding genius: the estimable John Harvey Kellogg, inventor of the corn flake, peanut butter and countless other nutritional icons, and director of the renowned (and nonfictional) Battle Creek Sanitarium, “the single healthiest spot on the planet.” A gleaming and prosperous spa, the “San” operates on a strict regimen of dietary restraint, exercise and inspirational invective. Guests include such luminaries as Henry Ford, Upton Sinclair, Thomas Edison and a generous assortment of rich neurotics such as Eleanor Lightbody and her husband, the dyspeptic and befuddled Will, who has followed her to the San in hopes of saving his marriage and his stomach both.

Also in town, on a very different mission, is the young wanna-be entrepreneur Charlie Ossining (Boyle shows, as always, a wondrous touch with names), who means to parlay a small borrowed investment into a brand new cereal company called Per-Fo. The arc of Charlie’s descent into the capitalist black hole of Battle Creek parallels that of Will Lightbody as he stumbles through the tortuous, hygienic corridors of the San (“a purgatory of the unwise and the unwell”), so that in time we begin to see each as a kind of shadow or double of the other--two small men of limited vision in this land of entrepreneurial giants. Their struggle to gain control over their respective fates propels the plot forward. Taken together with Dr. Kellogg, who strives to maintain his immaculate fiefdom, and his adopted son George, a poor man’s Frankenstein monster, the castoff demi-urge of a Promethean obsession, these earnest bumblers and lunatic pedagogues appear to be the perfect vessels for Boyle’s comic talents.

And yet the novel that results is something of a disappointment. For one thing, Dr. Kellogg’s head turns out to be an only fitfully rewarding place to spend time:

“The Doctor had triumphed, as usual, but at what cost? His stomach was sour, his joints ached, his eyes were tired. There were just too many troubles, too many things pressing on him, too many hands reaching into his pockets. Despite the rigors of the physiological life and the fortitude of mind and body it inspired, he was depressed. Tired. Overworked.”

With his triplicate syntax, his impresario’s cynicism and his dogged, humorless pedantry, the doctor is a tough nut to crack--and like George, he does not inspire much intimacy or affection from his creator. Or from us. For all his messianic fervor he comes across as a distant and hypocritical sadist; as when, to demonstrate to his patients the evils of meat, he tosses a steak to hungry wolf: “What he didn’t mention was that she had been trained, through negative reinforcement, to view meat as the prelude to a beating . . . or that her vegetarian diet had so weakened her, she wouldn’t have had the strength to chew it in any case.”

Then too, neither Charlie nor Will nor Eleanor--all victims of their own weak constitutions and the predatory designs of others--are, to put it mildly, terribly quick on the uptake. Because of this the story, untypically for Boyle, moves slowly, with every turn signaled well in advance. The pace may be in part a function of the setting, the dull uneventfulness of sanitarium life. Out of similar materials, of course, Thomas Mann built a towering philosophical novel, but Boyle has a very different set of intentions, and his trademark wit and inventiveness, his referential quickness, all seem oddly smothered here, as if they too have fallen victim, like Will Lightbody, to the San’s endless, static routine: “Another meal . . . but was it life, life as it was meant to be lived, raw and untamed and exhilarating, or just some glassed-under simulacrum? Will lifted the fork to his mouth, inserted a tasteless lump of roughage and sighed.”

Because the answer to Will’s question is never in doubt, there is not much in the way of thematic tension to sustain the reader’s intrigue. We are left with the considerable research Boyle has done into the period, which proves fascinating (I particularly enjoyed learning the alcohol content of the era’s various “tonics”) though not always dramatic. And after several hundred pages of colonic enemas, stool samples, meals of hash, nut bread and macaroni cutlets, and the good doctor’s hellfire sermons on nutrition and vegetarianism, the satiric edge gets a little blunt. There is an ambitious, pull-out-the-stops climax, and an extended coda that manages to be both deft and moving, but there are also times when the book reads like a Marx Brothers farce (“A Day at the Races,” say) minus Groucho, Chico and Harpo.

“The Road to Wellville” is craftily paved, but it is also somewhat longer and straighter than you’d expect. Boyle, who has delivered plenty of giddy rides in the past, seems to be relying this time on cruise control.