Unhallowed Ground by Paul Guernsey (Morrow: $16.95; 310 pp.)

Reading Paul Guernsey’s uneven but vividly imagined first novel, it’s difficult to shake the nagging feeling that this is a young adults’ book directed at grown-ups because of the sex, dope and violence it contains. Set in rural Connecticut, it is the story of a likable 17-year-old struggling to cope with a set of misfortunes dire enough to try the patience of Job, no less the troubled Moreno clan. Our hero, Manny Moreno, is afflicted with a missing father, a vacant and addictive mother, a scheming and stereotypical grandfather, and an unbalanced but clairvoyant sister who is cursed with the ability to foresee the Moreno tragedies from her perch atop an old sofa in the cellar of their ramshackle house near an ancient and beloved swamp.

Manny’s search for the secret of his father’s disappearance, and the concomitant burden of assuming his father’s role in the sickly Moreno household, are the themes of this hard-nosed and readable tale, which in fact would be perfect for young adults old enough to know that unpleasant things happen in the world, that good people sometimes do bad things, and that Holden Caulfield’s visit with a prostitute and Superman’s habit of flying out the window ought not to be emulated by interested readers.

In this case, Manny’s troubles have driven him to leave school and sit around the house until he eventually takes a job with the hated William Cahill, a wheelchair-bound magnate, and Lionel Barrymore doppelgaenger who retains both Manny and his strange friend, Toby Carver, as gardeners. Manny and Toby, who sometimes call one another “partner,” have a lot in common, including missing fathers, but their fates are tied more tightly than things at first seem.

It all has to do with the swamp, which is almost as much the hero of this book as Manny. That rapacious millionaire Cahill appears set on destroying this spooky wetland, and by extension, it appears, the natural order generally.

Cahill is unfortunately not much of a character, or rather he is entirely too much a character, and the same is regrettably true of Manny’s tiresome and long-winded granddad, whom the author has named Old Man Tarbox and whom he apparently recruited at the same casting call as the old man’s swamp-despoiling enemy and the local cardboard cops.

Another Guernsey weakness is dialogue. He displays little ear for it in “Unhallowed Ground,” and his characters sometimes talk like refugees from a sixth-grade reader:

“‘Yeah,’ Toby conceded. ‘You sure are a good fisherman, Manny. And you know all the spots out in that swamp. At least three times as many as I do.’ ”

Guernsey’s dialogue trouble is odd, because his prose is always clear and sometimes even sparkles. At its best, in fact, this is more a poet’s book than a philosopher’s, and Guernsey uses bright, hard images that make us see and feel things just as he imagines them. A cop has mirrored glasses like “twin TV screens,” and when Manny pulls a beer from its plastic six-pack membrane, it requires the same effort as “taking a slightly green apple from a tree.”

There is also decent suspense and riveting action--this is a species of murder mystery, after all--and some of the book’s 34 chapters would make fine short stories. Guernsey is particularly good on adolescents. His youthful characters are generally touching and true in their love, boredom and cruelty, as well as their depth of emotion, resilience and longing for escape.

But ultimately, “Unhallowed Ground” is a spotty mix of maturity and juvenalia, close observation and stock characters, gripping plot and implausible event. Guernsey is clearly a fine writer with great promise. Maybe in his next book, he can begin to fulfill the potential he shows in this one.