Red Earth, White Earth by Will Weaver (Simon & Schuster: $17.95; 514 pp.)

At the outset of this epic first novel, 30-year-old Guy Pehrsson, a transplanted Minnesota farm boy living the good life in Silicon Valley, receives a cryptic letter. Dated March 15, 1984, it reads in full: “Guy--Trouble here. Come home when you can. Sinceerly. (sic) Your grandfather, Helmer Pehrsson.”

“Trouble here.” It is the full meaning of Helmer’s typically laconic phrase that drives the plot and gives this novel its distinctive character. There is indeed trouble in spades back in northern Minnesota, as Guy discovers when he drives his Mercedes back to the family farm he left in disgust nine years before. Owned by his aging grandfather, operated by his alcoholic father Martin, the Pehrsson farm lies within the boundaries of the White Earth Reservation, land once granted to the Anishinabe Indians. Using underhanded tactics, white farmers and resort developers have acquired--over the course of a century--most of the prime Indian land. Now, led by Tom LittleWolf, a University of Minnesota Law School graduate and Guy’s childhood buddy, the Anishinabes are on the warpath, disputing white ownership of the land, making their case with politicians and in the courts but also using violent means to try to drive whites from the reservation.

It is the stuff of robust drama. And a resident of the northern Minnesota town of Bemidji, Will Weaver lives very close indeed to the arena of his fictional conflict. But if there’s trouble at White Earth, there’s big trouble at the dramatic center of this story.

A strange, almost shocking thing happens less than halfway into the novel: Weaver’s credibility, an impressive, smooth-running machine until then, suddenly hisses and shuts down like an overheated tractor. At a line as clear as the demarcation of the Great Plains from the Rockies, this once-promising novel breaks in two--the first part a grittily authentic, fascinating account of Guy Pehrsson’s youth, centering on his friendship with Tom LittleWolf; the second, a plot-heavy melodrama with characters as thin as onion soup.

This rupture, which begins with the arrival at White Earth of a Boston-bred, Yale-educated love interest improbably named Cassandra Silver, plucks us out of Minnesota--where Weaver has convinced us we are--and sets us down in the arid soil of Simon & Schuster’s ambitions for this Heartland Blockbuster, complete with posters for booksellers, “major marketing advertising” and “a major miniseries by the producers of ‘The Autobiography of Miss Jane Pittman.’ ” And it is nothing short of tragic.

It is tragic because Weaver, whatever his role in all the hype, is a writer of uncommon natural talent, a backwoods pitcher with a 98 m.p.h. fastball. Though his method is primarily photographic--he takes intriguing snapshots of most of his characters rather than revealing the inner workings of their minds--at his best, he’s that rare Real Thing, a writer writing eloquently, often between the lines but always with an undertow of passion about what he knows, where he lives, what he’s been through: “By March in Minnesota, houses, like barns and schools, had shrunken. Their late winter size depended on how well the inhabitants got along. In the waist deep snow, his (Guy’s) parents’ house was hardly bigger than a doll’s house.” Or: “Guy left the house. Outside he stood among the flax and watched the oncoming weather. Now waist-high and blooming blue on the higher swells of the field, the flax’s uncertain colors matched the sky. Southwest were the high, shining cumulous towers . . . . From the Northwest came the lower, darker, faster-moving clouds of the cold front. Guy for a half-hour watched the two fronts collide. Their clouds in slow motion churned and tumbled and rolled upward dark and bulbous. Supported now by yellow spider legs of lightning, the two fronts were no longer clouds but great spiders struggling for control of the reservation sky.”

Such sturdy, farmwise, sensuous writing typifies Part I, in which Guy and his “blood brother” Tom LittleWolf come of age and leave White Earth. Hitchhiking to California after rain and his grandfather’s stubborn refusal to harvest on a Sunday ruin the flax crop, Guy finds work in the computer industry. Eventually, he acquires his own circuit board company. It is this adult Guy Pehrsson--a tall, Nordic blond who drinks fine wine, romances Stanford Ph.D. candidates, subscribes to “Rose Grover’s Monthly” and drives a gray Mercedes--who returns to “trouble” at White Earth. And we arrive with him--in Part II--with great expectations.

But it’s a rude homecoming indeed--and not only for Guy Pehrsson. What had been serious fiction, the multidimensional illusion of real people in a real place, becomes fantasy, making this novel a strange ear of hybrid corn that certain producers and marketing specialists apparently have quite a taste for. One begins to feel rather bad for Will Weaver. Was it his idea to introduce the inevitably beautiful and “sexy” Cassandra Silver as a senator’s aide dispatched to buy off the Indians? Was it Weaver’s idea to transform a believable farm boy into a mythic, miniseries hero for the ‘80s--an entrepreneur, a two-fisted yuppie, a man of fewer and fewer words (and almost all of them enigmatic) who can get down and dirty in barroom and bedroom? (Sample dialogue--Cassandra: “You shoot and burn cars often?” Guy: “Not that much. Just when it seems right.”) Could it be the same Weaver who now gives us slick, one-dimensional senators, lawyers, bankers? The same Weaver who idealizes all the good guys (Tom LittleWolf, Helmer Pehrsson, et al.) by making them full-blooded, warm, emotional, in contrast to the bad guys (uniformly cold and calculating)?

If so, his heart’s not in it--or so it appears from the quality of the writing--from the contrived dialogue, the larger-than-life heroes and villains, the predictable, violent plot.

Why a novel that begins in dynamic colors faded to black and white is a question for speculation. “Will,” I wish some editor as fierce, stubborn, and proud as Helmer Pehrsson had written Weaver, “Trouble here in this novel. Stay home and keep writing about Minnesota. Forget New York. Forget Hollywood.”