By Josh Wolk
Updated February 10, 1999 at 05:00 AM EST

True to form, the latest John Grisham novel opens with a killer hook. Dressed in a green turban and white silk robes, the 10th-richest man in America scribbles his signature on a short, blunt handwritten will, then promptly leaps from a terrace 14 floors up. Gotcha! But if you think Troy Phelan’s gaudy exit and the disposition of his $11 billion estate will ignite yet another of Grisham’s skillfully tangled legal thrillers, forget about it. Before you can even say “probate,” ”The Testament” does a startling 180, turning into a slick but crotchety amalgam of ”The African Queen” and a Sunday-school parable.

Phelan, we soon discover, has stiffed his six greedy children — “a miserable bunch, all of them” — and left his fortune to a 42-year-old illegitimate daughter nobody knew existed. Stunned, the family and its brace of lawyers mount an immediate assault on the will. The designated heiress, meanwhile, remains oblivious to the hoopla. And if that seems a bit of a stretch — well, Rachel Lane happens to be a Christian missionary working with a tribe of Indians “somewhere” on the remote Brazil­Bolivia border. When Phelan’s attorney Josh Stafford decides to send an associate to find her and bring her home, the man he selects for the job is a middle-aged substance abuser with suicidal tendencies. Only in fiction, folks.

Naturally, O’Riley’s arduous river journey — like every other similar journey taken in the history of storytelling — will become a rite of passage. We expect our dissipated hero to find redemption through suffering, endurance, and the all-around lack of good hygiene. Ever the crowd-pleaser, John Grisham makes sure our expectations are fulfilled. Problem is, he does it so strictly by the numbers that after a while you realize that you’re not reading just a quest novel, you’re reading the quest novel. The generic quest novel. Isn’t it time, you think, for the outboard motor to conk out? And darned if it doesn’t sputter and stall, five sentences later. Shouldn’t O’Riley, you say to yourself, be getting lost in the dark right about now? Sure enough. Suspicious natives? Here they come. Finally, all you want is to be surprised — just a little. Doesn’t happen. Even Rachel Lane, when at last she makes an appearance, is precisely what you’ve been expecting her to be: a saint with a medical bag. Good-looking too.

What do you figure the chances are that Nate O’Riley will fall in love with her?

Exactly so.

Although ”The Testament” climaxes with some high-stakes dealmaking and a shrewd courtroom deposition (conducted by a spiritually renewed Nate), it all comes too late. Far too late. By then, you couldn’t care less who gets the old man’s billions. By then, you just want to scrape the swamp muck off your shoes, quit breathing soggy hot air, and get the heck out of this novel.