Following is a sample of the offerings, some old, some new, of boxed sets from mass-market paperback publishers : Isaac Asimov (Fawcett, $9.35). The five books of this boxed set cover the whole range of Asimov's science fiction carrer: Pebble in the Sky is his first novel, The Gods Themselves , a Hugo and Nebula winner; The caves of Steel is a celebrated sf-mystery featuring a robot and human detective working together. Two collections of short stories round out the set -- Nine Tomorrows and The Bicentennial Man.

The Earthsea Trilogy, by Ursula K. Le Guin (Bantam, $2.25). The central theme of all fantasy is education -- growing up and growing wise, encountering monsters at once real and symbolic of the inner conflicts that must be mastered to achieve a harmonious self. This great theme is charmingly reenacted in Le Guin's award-winning trilogy -- A Wizard of Earthsea, The tombs of atuan , and The Farthest Shore -- about the insturction, testing and final triumph of Ged. f

A Victorian Family, B M.V. Hughes (Oxford, $13.95). In this autobiographical trilogy, Molly Hughes evokes the texture of suburban middle class Victorian life. A London Child of the 1870s introduces us to her family's merry household in Islington. In A London Girl of the 1880s Molly becomes a teacher and falls in love with Arthur Hughes. In A London Home in the 1890s , she broadens her experience, traveling to America and the Continent and starting her own after her marriage to Arthur Hughes.

P.D. James (popular Library, $6.75). P.D. James' stories move with grace and decisiveness; her territory is psychology as well as mystery. Shroud for a nightingale, gives us two murders in a British school of nursing. In An Unsuitable Job for a Woman , Cordelia Gray, a young detective, is sent to investigate the apparent suicide of the son of a Cambridge don.Four corposes litter the scene in The Black Tower , before a murderer can be unmasked. When a famous mystery writer is found dead in Unnatural Causes , the seamay side of his life is revealed. Adam Dalgliesh is on hand to put together the puzzle in each.

The Palliser Novels, By Anthony Trollope (Oxford, $25). Thes six novels represent a triumph for the political novel. Together they trace the history of three major characters: the beautiful and lovable Lady Glencora Palliser; her husband Plantagenet Palliser, who becomes prime minister and later Duke of Omnium, and finally, Phineas Finn, an Irishman who wins a seat in Parliament, a place in society and, eventaully, happiness. Trollope has reconstructed the intricate world of 19th-century British politics and society, peopling it with a vasty array of memorable characters. This set of paperbound facsimilies of the Oxford classics is extremely handsome.

Zane Grey (Pocket Books, $7). Zane Grey practically invented the western novel. His 60 books sold 13 million copies during his lifetime; since his death in 1939 they have sold millions more. Here are four novels that chronicle cowboy life -- Forlorn River, Drift Fence, Western Union and Boulder Dam . Who would tamper with their formula?: selfreliant, brawny hero struggles against the infamous villainy of thugs while chivalrously courting a naive heroine.

George Eliot, (Pengiun, $40).All seven novles plus Scenes of Clerical Life by that strong minded, brilliant rebel of the 19th century are included here. Born in 1819 as Mary Ann Evans, Eliot signed her writing with a man's name hoping to excape the myriad conventions restricting what women might respectably think. Her heroines, especially Dorothea Brooke of Middlemarch , were clear-sighted intelligent women often burdened with men who were just the opposite. Not a revolutionary but rather a quiet seeker after freedom and excellence, George Eliot's elegantly detailed plots and deep sense of morality are both refreshing and needed in our times. This strongly boxed 8-volume set is made to last -- as it should be.

John Steinbeck, (Penguin, $8.80). Steinbeck, who won the Noel Prize in 1962, is best-known for The Grapes of Wrath , his epic novel of the Joad family's journey out of the dust bowl of Oklahoma to the promised land of California. Among the shorter works also included here is Of Mice and Men .