The Fountain and Other Fables, by Frederick Morgan (Pterodactyl Press, Main Street, Cumberland, Iowa, 50843, $15; cloth $20). For Frederick Morgan -- a distinguished poet and editor (The Hudson Review) -- the fable is a blend of fairy tale and prose poem. In his pleasing book the reader will meet a princess whose moods and appearance change with every day, a magical wood where ''a ballerina who went sleepwalking by moonlight was adopted by the grimacing dwarves as their queen,'' and where a little girl with her scissors and some large sheets creates a race of paper people. The language throughout is simple yet apt, and the whole book redolent of Laforgue and Kafka, of Grimm and Sendak.

A Voyage to Arcturus, by David Lindsay (Citadel, $5.95). The publisher has saddled this uncategorizable novel with a lurid cover calculated to seduce aficionados of bug-eyed monster science fiction. Ignore it; A Voyage to Arcturus is a potent and compelling novel of ideas which, since it was first published in the early '20s, has attracted an impressive coterie of admirers (among them Santayana, Frank Lloyd Wright, and Harold Bloom) with its hair-raising Blakean visions. Its hero is transported to a distant world where his increasingly bizarre and unsettling adventures align to form a kind of Pilgrim's Progress in which Lindsay ponders the problem of suffering and eviROMAN and William Gass' recent extollation of The Fifth Queen, Ford Madox Ford's reputation is on the upswing. The Tietjens tetralogy (Parade's End) also has its champions, but Ford himself considered The Rash Act his best book. Written in 1933, when he was 60, it displays Ford's characteristic technical mastery in telling the story of a man whose suicide attempt culminates in his assuming a new identity. Lighter than Ford's other masterpieces, it is a novel that basks in the sun-lit languor of his favorite corner of the earth -- southern Francce. Readers intrigued by Ford and his work should be sure to look for Carroll & Graf's reprintings of two of his novels written with Joseph Conrad: Romance and The Inheritors (both, $7.95). The latter is in part a proto-science-fiction tale about the ''Dimensionists,'' the race that will supersede mankind.

Cotton Comes to Harlem and The Crazy Kill, both by Chester Himes (Allison & Busby, $5.95 each). For sheer toughness it's hard to beat the black detectives Coffin Ed Johnson and Grave Digger Jones. Himes never received the recognition he deserved for his books -- the combine elements of George V. Higgins, Elmore Leonard, and Richard Stark, with a bleak vision all their own -- and it is good to have them available again, especially as they are gritty depictions of black life in New York at least as much as they are expertly-paced thrillers.

Where the Rivers Flow North, by Howard Frank Mosher (Penguin, $5.95). Northern Vermont is where. These five short stories and a novella feature country people whose occupations center on the logging industry and whose lives tend to cluster at the unfortunate end of the spectrum. But the characters have dignity and power nonetheless, and Mosher writes about their lives, customs, and environs in loving detail. One story begins with this evocative sentence: ''Banked up snug against the stone foundation of a farmhouse, spruce boughs will catch and cradle the first hard snow of the year and hold it all winter, turning a cold wind and keeping in stove warmth better than any expensive sixing you can name.''

The Belton Estate, by Anthony Trollope (Dover, $7.50). No summer would be complete without at least one Trollope novel to look forward to -- and Dover has supplied this season's treat. In this one, the reader finds himself caught up in a roundelay of Victorian love affairs, matches, and mismatches, all of them whirling about a large inheritance and estate. Who will marry whom? And, just as important, who will get the money? As usual, Trollope remains the 19th-century's answer to Masterpiece Theatre. NONFICTION

On the High Wire, by Philippe Petit; foreword by Marcel Marceau (Random House, $11.95). The author is the high-wire artist who performed for one hour a decade ago on a cable strung between the twin towers of the World Trade Center in New York City. Of course he has accomplished many similar feats of daring. In this eloquent and beautifully illustrated tribute to his dangerous art, Petit tells its secrets, one of which is, ''I am never afraid on the wire. I am too busy.''

A Strange Virus of Unknown Origin, by Dr. Jacques Leibowich (Available Press/Ballantine, $4.95). A young French immunologist who first consulted on a case of AIDS over a decade ago, Leibowich is well known on both sides of the Atlantic. In an introduction to his volume, which was translated by the poet Richard Howard, Dr. Robert Gallo of the National Cancer Institute calls Leibowich ''highly instrumental in stimulating scientists to work just a bit harder to solve the AIDS riddle.'' He writes in a colloquial, often colorful style, but the chopped-up format, unfortunately, detracts from the sense of information flowing smoothly from expert to layman.