Better To Joke Than to Hang BERNARD SHAW, COLLECTED LETTERS: 1926-1950 Edited by Dan H. Laurence; Viking; 946 pages; $45 MARK TWAIN'S LETTERS: 1853-1866 Edited by Edgar Marquess Branch, Michael B.

By Stefan Kanfer

Two extraordinary publishing enterprises greet each other this month, just as their subjects did more than 80 years ago. The final entries in George Bernard Shaw's four-volume, 76-year-long correspondence present the master playwright bombinating into old age, dispensing unsolicited advice on every aspect of modern life from the flaws of the cinema to the indignities of sex. The first of a projected 20 volumes of Mark Twain's letters follows the literary apprentice -- at first still using his real name, Samuel Clemens -- as he flees Hannibal, Mo., to become a river pilot, then a journalist covering the gold-intoxicated frontiers of Nevada and California.

On the surface the two writers, separated by time and culture, seem wholly unrelated. The American is a sensual naif; the Anglo-Irishman is a sophisticated puritan. Twain is happy for small favors; Shaw is ungrateful for major rewards. Presented with the 1925 Nobel Prize for Literature, Shaw informs the Royal Swedish Academy that their award is a "lifebelt thrown to a swimmer who has already reached the shore in safety." Shaw's dramas brim with advocates of free thought and liberal policy, but his correspondence reveals him as a fool of the new totalitarians. Adolf Hitler is a "wonderful preacher of everything that is right and best in Toryism"; Joseph Stalin is the "greatest living statesman."

In contrast, Twain's letters show a simmering distaste for politicians and a maturing affection for the family he left behind. When his younger brother Henry is fatally wounded in a steamboat explosion, the youthful Clemens rushes to his side. He "prayed as never man prayed before," he writes his sister, "that the great God . . . would pour out the fulness of his just wrath upon my wicked head, but have mercy, mercy, mercy upon that unoffending boy."

From mining country, Clemens writes his mother that the land is "fabulously rich in gold, silver, copper . . . thieves, murderers, desperadoes, ladies, children, lawyers, Christians, Indians, Chinamen . . . poets, preachers, and jackass rabbits." A sister receives more intimate intelligence: "I don't mind sleeping with female servants as long as I am a bachelor -- by no means -- but after I marry, that sort of thing will be 'played out,' you know."

Given the disparities of tone and temperament between them, could Twain and Shaw have tolerated each other's company? Later volumes will disclose what Twain thought when they met in the early 1900s. For his part, Shaw recalls that the American exhibited a "complete gift of intimacy which enabled us to treat one another instantly as if we had known one another all our lives." The common ground was their nearly identical comic techniques. Both men, Shaw acutely perceives, "put things in such a way as to make people, who would otherwise hang us, believe that we are joking." Twain leads the reader on, plausibly and gently, until he can spring his trap. After his mother harangues him about the benefits of exercise, he joins a San Francisco health club. "I sleep better, I have a healthier appetite," he assures her. "I feel as if I ought to be very well satisfied with this result, when I reflect that I never was in that gymnasium but once in my life, & that was over three months ago." Shaw places a sting in the tail of a compliment. Visiting William Randolph Hearst's ostentatious ranch in California, he decides, "This is the way God would have built it, if He'd had the money."

Both writers develop similarly clownish personas to guard their private selves. Shaw cautions a potential biographer, "I am not really a good subject, because all the fun that is to be got out of me I have already extracted myself." Then he bows to his predecessor: "You can't write a funny book about Mark Twain" because he has "been there before you and reaped the field too thoroughly to leave any gleanings."

The editors of these delightful volumes have ignored the warning. Nearly 1,000 brilliantly annotated letters present humorists with a cornucopia, psychologists with the darker sources of comedy, and students with the intimate prose styles of the rich and famous. As for the rest of the audience, they are provided for as well. After all, what reader has ever been able to resist a look at other people's mail?