The cover art is bold; the 6-by-9-inch size, substantial. The paper, thick and white; typography and design are elegant. The books that share this handsome format inaugurate an ambitious paperback series, ''Aventura: The Vintage Library of Contemporary World Literature.'' American readers have lately made best sellers of more than one foreign ''literary'' novel, a phenomenon the editors of Aventura regard as evidence of an increasing ecumenism in reading tastes. They propose to serve up for this taste a cornucopia of serious fiction, belles-lettres, and poetry by contemporary writers from all parts of the world. Aventura will publish six to eight books every spring and fall. Some, such as the Salvadorean novel ''One Day of Life,'' will be appearing for the first time in English. Reprints of acclaimed hard-cover books - ''Ake'' and ''The Questionnaire,'' both published in 1982 - will make up the rest of the list.
Other publishers have made a practice of introducing foreign authors to American readers in paperback form. Our current love affair with Latin American writers in particular, owes much to Avon's Bard imprint. Nobel laureate Gabriel Garcia Marquez found an American audience largely by word of mouth after Bard's publication of a mass-market edition of ''One Hundred Years of Solitude.'' Before Bard, New Directions brought the work of Borges and Mishima, among others , to America. Penguin continues to expand a distinguished international paperback list. These houses have concentrated on publishing individual authors and have maintained a flexible and receptive stance toward work of distinction, regardless of geographic origin.
Aventura's difference is its studied internationalism. Every publishing season Aventura will present a list that ''will aim fairly to represent all parts of the globe'' (presumably, all races, colors, creeds, and sexes, too). Nonfiction and genre publishers routinely establish categories, target audiences , and solicit or commission books to fill the slots of each list. That approach, while unorthodox for literary publishing, may be judged by the quality of the books it brings to print.
''One Day of Life'' tells of a 12-hour excursion to a rural village populated largely by women in war-torn El Salvador. Author Argueta is a poet as well as a novelist, and his prose often rolls in lyric waves. ''Then the sky becomes clear as well water at high noon. Little bits of colored glass. Chips from a broken bottle. And clouds floating under water.'' The voice is Lupe's. A grandmother at 44, her meditations constitute the novel's core as she awakens and begins her chores.
''The sky turns the color of the blood of a dead bird.'' In her rural village of Chalete, violent disorder has become the daily order; corpses, a regular feature of the landscape, so that even dawn is cloaked in a sinister image. Lupe usually awakens alone. Since Chalete's men took part in a protest over fertilizer prices, the Civil Guard has waged a decimating vendetta against them. Lupe's husband hides in the hills each night. Men who do not, turn up dead, or they do not turn up at all.
Day goes by and Lupe's thoughts turn to the changes that have come to Chalete in her lifetime: the radicalization of the Roman Catholic clergy; the political activism of her children and grandchildren; her own dawning awareness that grinding poverty may not be the lot she must simply accept. Lupe reflects upon the violence that peasant agitation for rights and reforms has provoked. Soldiers murdered and decapitated her son, Justino; son-in-law Helio has ''disappeared.'' By day's end the most grisly atrocity of all will have been visited on Lupe's hut. Nevertheless, she can say, '' . . . we're having a better time of it. Why better if they beat us more than ever? Because now we know where we're headed.''
This sense of righteous collective purpose is the book's central theme and its greatest handicap. When Lupe and other family members slip from singular rumination into pluralistic lecturing, the spell of the fiction is broken. Characters turn to cardboard; meditations degenerate to the harangues of pamphleteers. The Salvadorean government has banned this novel; Argueta lives in exile. These news items add drama to the book's release in the United States; they do not necessarily imply either literary merit or truth. Works of social protest are rarely balanced and even more rarely, works of art. ''One Day of Life'' is riddled with bombast, but its finest passages - Lupe's random associations on the ethos of dogs, for instance - evoke powerful images of a people and land most of us know only marginally, although that people's destiny is closely linked, at least for the moment, to our own.
Wole Soyinka, a Nigerian, is another whose writing often carries a political message. Plays, poetry, and criticism have included scathing indictments of foreign and domestic corruption. He decries the erosion of Yoruba culture and is critical of American and European values that have spread with commerce in his oil-rich country. The tone of his memoir, ''Ake, The Years of Childhood,'' is, in contrast, pastoral.
Soyinka was raised the son of educated Christian parents in the parsonage compound of the western Nigerian town Ake. His father taught at the Anglican school and served as unofficial leader of the town's intellectual community. His mother kept a shop in the main town beyond the parsonage walls; she served as stepmother, also, to the children sent to the parsonage to live and attend school.
Soyinka conjures up that region of mingled myth and reality which children early inhabit. His language is often mesmeric. ''On a misty day, the steep rise toward Itoko would join the sky. If God did not actually live there, there was little doubt that he descended first on its crest . . . .'' Three-year-old Wole's misperceptions are a matched set with the primitive sensibility of tribesmen outside the parsonage wall who see spirits everywhere and omens in the fall of a leaf.
''Ake'' is filled with memorable people. Beyond the author's father and mother, Essay and Eniola, or ''Wild Christian,'' as she is known, Bukola, the otherworldly Abiku child, and Father, Soyinka's pagan grandfather, are permanently etched in my mind. The scene of ritual ankle and wrist carving to which Father treats his grandson is one of the most powerful in the book. Gradually, young Wole grows to distinguish the real from the imaginary and to discover how things work. Just as gradually, Nigeria leaves behind its native culture and spirits to enter the community of modern nations. Soyinka's memoir is a straightforward account of his and his country's parallel coming of age in the years immediately before and during World War II. He neither seeks nor discovers the elusive link by which some memoirists bring the invisible past into coexistence with the tangible ''now'': ''Ake'' does not concern itself with questions of relativity or metaphysics. Through vivid accounts and loving renderings Soyinka serves us the familiar events of childhood - first days at school, rivalries both sibling and filial, forbidden explorations, birthdays - in an exotic setting.
If Soyinka remembers the phantasmagorical regions of childhood, Jan Chrysostum Kepka, visionary hero of Czech writer Jiri Grusa's ''The Questionnaire,'' never left them. His story is as deeply rooted in his native Chlumec as is Soyinka's in Ake and Lupe's in Chalete; unlike their towns, which could be nowhere but in Nigeria and El Salvador, Chlumec could be anywhere. It is a state of bedazzled mind.
Jan Chrysostum, sometime painter, gardener, soldier, well driller, has applied for 15 jobs since being placed on a list of political undesirables, all to no avail. Upon applying for Job 16 - flag and poster designer for the enterprise Granit in the city of Prague - he receives the same questionnaire. The Granit questionnaire is different in one respect; someone, probably the interviewer, has scribbled a blue penciled exhortation across the top: DO NOT CROSS OUT. Jan Chrysostum, desperate and imaginative enough to see the hand of providence at work here, considers the message highly significant, an omen. ''None of the Comrades with whom I had dealt before felt any need to elaborate on the bare questions or prescribe any particular method for filling out the form.'' Inspired by such unmistakable encouragement, Chrysostum launches into the questionnaire determined to cross out nothing and to reveal all.
Class origins, language skills, love affairs, property - fixed and movable: No question is so mundane that it does not send Chrysostum careening down some Chlumec alley of his past, present, or future, trotting out parents Edvin and Alice, bureaucrat Uncle Bonek, childhood heartthrob Erna, and dream interpreter Cousin Olin. A wackier crew you will not encounter; like-minded individuals populate the books of Nabokov, Grass, and Garcia Marquez, to whom Grusa may be compared. These writers images do spring initially to mind, but they quickly fade, so enchanting is the voice of the inspired lunatic so compelling his fabulous story.
Aventura's initial offering is a mix of the au courant and authentic art. Three more books will appear next month, Brazilian Darcy Ribeiro's ''Maira,'' Austrian Thomas Bernhard's ''Correction,'' and ''Masks,'' by Fumiko Enchi of Japan. This is an impressive debut and bodes well for readers who welcome fine literature, whatever its geographic pedigree.