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.