My "Mark Twain's Auto-biography", with an introduction Albert Bigelow Paine,
editions were copyright in 1924 - - the Harper & Brothers Publishers K-Y edition.

There is also "The Autobiography of Mark Twain" edited by Charles Neider.
Last, but not least, you may want to read "Mark Twain's Autobiography and
First Romance" -a burlesque autobiography
that is most entertaining and very much Twain.