CHATTERTON By Peter Ackroyd Grove. 234 pp. $17.95

THE FAMILY ROMANCE OF THE IMPOSTOR-POET THOMAS CHATTERTON

By Louise J. Kaplan Atheneum. 301 pp. $24.95

THOMAS CHATTERTON (1752-1770) was not just a teen-age suicide before the phenomenon. He had a kind of genius. Not at poetry per se, for though he wrote reams of it, his oeuvre is flashy but shallow. No one except scholars reads him now, and even when he was alive it took adeptness at Middle English to get through his pseudo-archaic diction without faltering. Not at literary forgery, either, though he is celebrated for that. Horace Walpole, himself no mean fraud, pronounced the boy a huckster almost at once.

Yet Coleridge wrote "A Monody on Chatterton," and Keats dedicated Endymion to him. Shelley and Byron mentioned him in their writings, and Wordsworth gushed over him as "the marvellous Boy,/ The sleepless Soul that perished in his pride." Even the redoubtably sensible Dr. Johnson called him "the most extraordinary young man that has encountered my knowledge." His gift was for the quite modern achievement of outrageousness, and he served as an English precursor to the Romantic poe`tes maudits, who burnt themselves out like skyrockets and left legacies of incandescent lyrics written at top speed. Keats, Byron and Shelley all went to their graves young, and Rimbaud wrote his great poems before the age of 20, but no one has equalled Chatterton's feat of death and transfiguration at 17 and a half.

Clinical psychologist Louise Kaplan might have called her psychobiography Young Man Chatterton, in homage to Erik Erikson's Young Man Luther, after which it seems to be modeled, if it weren't that young manhood was as far as Chatterton got. Without meaning to trivialize her book, which combines meticulous scholarship with shrewd and mostly jargon-free insights into the dynamics of imposture, I can't help but consider it the ideal prologue to Peter Ackroyd's witty, tricky new novel.

Chatterton was born in Bristol to a widowed mother. His father, chorister to the local church, had died three months after the child's conception. Thomas grew up indulged by the women in his family but straitened by economic reality. At 15 he left school and signed on as apprentice-scrivener to an attorney. By placing a premature suicide-note where it was sure to be found, he escaped the mundane career decreed for him and migrated to London with everyone's blessing.

In the meantime -- and essentially unknown to his family -- he had written thousands of lines purported to be the newly-discovered work of the (imaginary) 15th-century priest Thomas Rowley. Couched in Chatterton's pastiche of Chaucer and other medieval sources and indited on parchment the elder Chatterton had pilfered from church, the poems glorify Bristol's past, considerably elevate the Chatterton lineage, and lionize Sir William Canynge, the actual benefactor of that same church. According to Kaplan, this canard served to endow its perpetrator with the patrimony he lacked.

It also fetched him just enough income from gullible patrons to lead him to think he might make a living by his pen. In London he stooped to journalism and pamphleteering, turning out satirical and pornographic screeds in the manner of his hero, anti-royalist reformer John Wilkes. But not even this strategy paid. Despairing and broke, the boy swallowed arsenic one night and was found dead the next morning. (In an irony he might have enjoyed, the famous portrait of him newly dead hanging in the Tate Gallery -- and reproduced on the cover of both these books -- turns out to be a fraud. Without access to the sole surviving likeness of the youth, the painter engaged the future novelist George Meredith as a model.) His works were saved and published, and a generation later the Romantic movement annexed him.

Ackroyd, author of the novel Hawksmoor and a biography of T.S. Eliot, populates his contemporary takeoff on the Chatterton phenomenon with a medley of eccentrics. There is Charles Wychwood, a feckless poet who unearths an alleged portrait of Chatterton at age 50 in an antiquarian bookshop and obtains a Chatterton manuscript from an elderly gay couple in Bristol. Doubting Thomas as he has come down to us in history, Wychwood scents the literary jape of all time: Chatterton may have faked his suicide and lived on in prosperous obscurity, ghosting many of the great Romantic poems.

THERE IS Harriet Scrope, wizened minor novelist, who refers to herself as Mother, swears profusely, downs straight gin and sticks her tongue out at Charles' young son when no one else is looking. Eventually, she tries to cash in on Charles' sleuthing. There is also Stewart Merk, secretary and protector, who, when his artist-employer could no longer uncrimp his arthritic fingers, took up the brush.

Deceptions abound. Harriet Scrope borrowed most of her plots from the novels of a Victorian hack. Even the bird on her favorite hat is ersatz, as her cat Mr. Gaskell discovers when it falls off and he pounces. The multiple unmaskings occur against a backdrop of scruffy flats filled with woebegone artists and poets manque's that Ackroyd delineates with caustic exaggeration. I particularly liked the iconoclastic new movement, Art Brut.

Ackroyd hoards some of his best tricks for the end, and Chatterton himself chimes in periodically to voice the author's best guess as to his veridical fate. The real Chatterton may have been less "marvellous Boy" than Zeitgeistmeister, but Peter Ackroyd's Chatterton is the genuine article, a contrivance of the highest order.

Dennis Drabelle is a Washington writer and editor.