the truest of all books; for while it inevitably consists mainly in extinctions of the truth, shirkings of the truth, partial revealments of the truth, with hardly an instance of plain straight truth, the remorseless truth is there, between the lines, where the author-cat is raking dust upon it which hides from the disinterested spectator neither it nor its smell … the result being that the reader knows the author in spite of his wily diligences.

Howells replied skeptically, “Even you won’t tell the black heart’s-truth. The man who could do it would be famed to the last day.”

Howells was correct. In the end, Sam failed to tell the whole truth and nothing but the truth about his life in his memoirs. From the beginning, he was reticent to discuss sex, for example. “There were the Rousseau confessions,” he acknowledged, “but I am going to leave that kind alone.” He eventually conceded to Howells that “as to veracity,” the entire autobiography “was a failure; he had begun to lie, and that if no man ever yet told the truth about himself it was because no man ever could.” Sam elsewhere declared that “no man dares tell the truth until after he is dead.” His autobiography is so rife with inaccuracies, embellishments, exaggerations, and utter untruths that a cottage industry of naysayers has developed to debunk it. Many parts contain not so much a remembrance of things past but a remembrance of things that did not happen. As Louis J. Budd remarks, scholars who try “to separate truth from yarn-spinning in his autobiographical dictation” have discovered it is “a mountain of funny putty.” Sam Clemens’s biographers must consult the autobiography with caution in reconstructing the events of his life. He never allowed the facts to interfere with a good story, such as the discovery of a blind lead in Roughing It (1872) or his complicity in the death of a stranger in “The Private History of a Campaign that Failed” (1885). Even the apologetic Paine admitted that Sam’s autobiographical dictations bear “only an atmospheric relation to history.” Bernard DeVoto agreed that though he was one “of the most autobiographical of writers,” he was “least autobiographical” when he tried to chronicle his life. Howard Baetzhold describes Sam’s memory as “faulty” and “convenient,” and Hamlin Hill calls it “immensely selective.” James M. Cox refers tactfully to “the magnifying lens of his imagination.”

More here.