The apocalypse according to Malamud; God's Grace, by Bernard Malamud. New York: Farrar, Straus, & Giroux Inc. 223 pp. $13.50.

There are tales of the beginning of things: Genesis, for example, and ''Paradise Lost.'' There are tales of the ending of things: Revelation, for example, or ''Die Gotterdammerung.'' Bernard Malamud's latest novel is both of these. It concerns a beginning and an end.

Or rather it begins with a Day of Devastation, the final thermonuclear holocaust when the ''Djanks and the Drushkies do themselves (and the world) in, '' and it ends with a new world aborning, the dawn of another day, a myth of creation.

In between the world's end (Chapter 1) and its beginning (Chapter 6), ''God's Grace'' recounts the story of the last man on earth, a paleologist named Calvin Cohn, who was down in a diving bell at sea's bottom, and so missed man's final curtain. When scientist Cohn, a rabbi's son, resurfaces to his oceanographic mother ship, he beholds in horror the sky ''smeared with ashes and the reflection of flames.'' Recovering slightly, he begins to say Kaddish for names picked at random from the New York telephone directory.

At first it looks as if Malamud has in mind a latter-day Robinson Crusoe. Last man Cohn finds a desert island and begins to stock it with salvaged ship's stores. A Shakespeare, a Bible, a small encyclopedia, a tool chest, clothing, provisions, a portable windup phonograph. But no, Malamud intends no modern bourgeois epic of self-sufficiency and survival. He is after bigger game.

Malamud's protagonist begins his saga in a talk with God - about covenants, about the Flood, about first and last things - and continues his tale by teaching speech to a colony of late-blooming chimpanzees. Would you believe a chimp with a German accent? ''Onimals con talg. We talg among ourselves. Maybe someday you will hear our phonemes oz we hear yours.'' And would you believe a lady chimp with a lisp? ''I wuv you.''

As Cohn's tropical island gradually populates with simian survivors of the Devastation, Cohn finds himself the manager of a nest of budding geniuses. He lectures daily on everything from dinosaurs to ''Romeo and Juliet.'' He names his chimps ''Esau,'' ''Ephraim,'' ''Saul of Tarsus.'' Baboons take names like Sara and Hattie. There is a lady chimp named Mary Madelyn. A gorilla named George.

Will the new earth become a jungle gym? Animals replacing men? A planet repopulated by the apes? Malamud provides no easy answers. Things look Edenic at first, but soon there is trouble in Paradise all over again, and Cohn, despite the most pacific of intentions, finds himself with a full-scale rebellion on his hands. How violence and sexual jealousy reenter this Talmudic wonderland let each reader discover for himself. Suffice it to say that Malamud, whose previous fiction deals in large part with race relations (''The Fixer,'' ''The Tenants,'' ''The Magic Barrel''), believes the world turns on a few eternal verities, and that the more things change the more they remain the same.

''God's Grace'' is both a sobering and a cheering tale. Malamud tells with humor and a grace of his own a tragi-comic parable, somewhere east of sci-fi, somewhere west of allegory. ''God's Grace'' is both an old-time morality play and a new hard look at the nature of miracles.

T. S. Eliot thought the world would end, ''not with a bang but a whimper.'' Bernard Malamud has a better idea.