If Not Now, When? by Primo Levi (Penguin, $6.95). Since he retired from his career as a chemist to devote himself fulltime to writing in 1977, Primo Levis' reputation as one of Italy's most important writers has steadily grown. A survivor of Auscwitz, Levi has chosen to write primarily about events of World War 11 in both his fiction and nonfiction. This novel is based on a true story Levi heard in Milan after the war, about a band of Eastern European Jews who had operated as guerrillas along the borders of Poland and Russia. During the winter of 1945, they had made their wayb to Italy, a first step toward Palestine. Levi, who knew nothing first hand of their lives as partisans, does a masterful job of constructing their world of constant danger and movement. There is romance, adventure and even humor. Crampton Hodnet, by Barbara Pym (New American Library, $7.95). A merry farce of a novel, writen by Barbara Pym early in her career, but published posthumously, Crampton Hodnet is one of her least complex works and also of her most purely funny. The setting is North Oxford, the characters a daffy bunch of eccentric dons and their families, the action a series of romances and near misses that leaves one laughing out loud. NONFICTION

Orbiting the Sun: Planets and Satellites of the Solar System, by Fred L. Whipple (Harvard, $7.95). Jupiter's mass is mor than 300 times Earth's; Venus' surface is some 457 degrees Centigrade and is blanketed by the weight of 90 Earth atmospheres, mostly carbon dioxide; Saturn's rings are composed of minute particies of matter. The author is professor emeritus of astronomy at Harvard; he writes crisp non-technical prose and shows the reader around the solar system rather like a proud gardener showing off his plants. My Friend, My Father, by Stanley Burnshaw (Oxford University Press, $7.95). Stanley Burnshaw, a poet and publisher, wrote this affectionate memoir of his father Ludwig Burnshaw in 1981. The senior Burshaw emigrated to the United States from a Latvian ghetto and after attending Columbia became well known in the first half of this century as an inovative educator, particularly for his orphangage and school in Pleasantville, New York. The son's chronicle records the humane ideals of an older generation and how its members preserved their idealism in the teeth of ferocious anti-Semitism abroad. The Four Seasons of Shaker Life, by Gerald C. Wertkin; photographs by Ann Chwatsky (Simon and Schuster/Fireside, $12.95). In the stark beauty of Shaker life and artifacts there seems to be something at once fundamentally American yet ethereally beautiful. A chair, a pitcher and wash basin, a house, an apple -- all these share a simplicity that suggests a harmony with nature and spirit that is easy to envoy. But few are strong enough to emulate. In this album Gerald Wertkin offers a portrait of the Sabbathday Lake, Maine, community -- the sole Shaker group still following the traditional practices -- while Chwatsky's photographs capture the quiet beauty of this profoundly religious people. Bayonets to Lhass and The Siege at Peking by Peter Fleiming (Oxford University Press, $8.95 each). You're read Ian Fleming and know the exploits of his hero James Bond; now read his older brother Peter whobas journalist and amateur historian wrote travel and adventure books about the mysterious lands east of Suez in the palmy days of Empire. These two adventures positively palpitate with Kipling-esque excitement: in the first, Colonel Francis Younghusband in 1903-4 leads a British expedition through the defiles of the Himalayas to Lhasa, upstages the Russians in the Great Game and persuades the Tibetans to sign a friendship treaty, only to have London reject the agreement. In the second, Her Majesty's minister in Perking withstands the siege of the Boxes for 55 days until an allied relief force routs the xenopholic Chinese. Between Meals: An Appetite for Paris, by A.J. Liebling (North Point, $10.95). This lovely book -- the need New Yorker journalist's last -- belongs on the short shelf with the gastronomic memoirs of M.F.K. The taste of Tavel, the importance of being poor in the education of an eater, a year spent in Paris as a student, praise for Waverly Root's clasic The Food of France, laments for the passing of the golden age of French restaurants, vignetes of gouirmands, restauranteurs, courtesans -- all the usual elements are here, depicted in sprightly, exact prose. Here is a taste of Liebling to whet the appetite: "Like the Norman, Calvados matures slowly and pays no taxes, but it is full of craft . . . "For more good writing, do not miss James Salter's introduction, part appreciation, part autobiography. Otherwise Engaged: The Private Lives of Successful Career Women, by Dr. Srully Blotnick (Penguin, $7.95). A research psychologist, Srully Blotnick has made something of a name for himself examining how people succeed professioinally and what happens to them when they do. The Corporate Steeplechase charted various paths to the executive suite. This book concentrates on working women, asking the perennial question: What price success? Blotick, in his study of 3,000 subjects finds that many successful women feel they have missed out on a personal life, have few meaningful relationship and find it difficult to maintain those they do have. Blotnick discovered that the most ambitiouis women often fared worse in both their professional and their persoal lives. CHILDREN'S

The Pilot & the Lion Cub: Odd Tales From the Smithsonian, by Peggy Thomson and Edwards Park (Smithsonian Institutio Press, $4.95; ages 10-14). In the fabulous collections of the nation's attic, the bizarre and the exotic abound. Here is a delightful collection of little known facts about some of the exhibits, and how they arrived at the Smithsonian, e.g. Lindbergh's grandfather's dog's dentures. The title refers to a perfectly respectable stuffed lion who when alive belonged to an aviation pioneer named Rosoce Turner. The Swineherd, by H.C. Andersen and Lisbeth Swerger (Picture Book Studio, $5.95; ages 4-8).). The tale is classic -- that of the unsuccessful wooing of a princess by a poor prince. The illustrations, soft, colorful and fresh, give new life to the story of a spoiled girl and her suitor's revenge. Listen Children: An Anthology of Black Literature, edited by Dorothy S. Stickland with a foreword by Coretta Scott King, illustrated by Leo and Diane Dillion (Bantam, $2.95; ages 6-12). This is a marvelous little book, an excellent introduction to the work of many black writes including Langston Hughes, Maya Angelou, Gwendolyn Brooks, and Nikki Giovanni among others. Included are poems, memoirs, stories, folktales, and biography -- all chosen carefully to mirror a culture and to entertain.