MR. CLEMENS AND MARK TWAIN by Justin Kaplan. 424 pages. Simon & Schuster. $7.95.
Mark Twain was as conscious of posterity as any other writer who ever anticipated its judgment. He saved the thousands of letters that came his way and expected his correspondents to do the same (they did). Before his death at 74 in 1910, he commissioned an official biographer, Albert Bigelow Paine. A large portion of Twain's estatethe fragments, stories, notes and autobiography unpublished during his lifetimehas since been paid into print by his literary executors. Yet none of it...