| Hollow Tree Nights and Days | English | January 23, 2008 |
| Mark Twain's Letters — Complete (1853-1910) | English | September 19, 2004 |
| Mark Twain's Letters — Volume 1 (1853-1866) | English | September 18, 2004 |
| Mark Twain's Letters — Volume 2 (1867-1875) | English | September 18, 2004 |
| Mark Twain's Letters — Volume 3 (1876-1885) | English | September 18, 2004 |
| Mark Twain's Letters — Volume 4 (1886-1900) | English | September 19, 2004 |
| Mark Twain's Letters — Volume 5 (1901-1906) | English | September 19, 2004 |
| Mark Twain's Letters — Volume 6 (1907-1910) | English | September 19, 2004 |
| Mark Twain: A Biography. Complete | English | October 4, 2004 |
| Mark Twain: A Biography. Volume I, Part 1: 1835-1866 | English | October 4, 2004 |
| Mark Twain: A Biography. Volume I, Part 2: 1866-1875 | English | October 4, 2004 |
| Mark Twain: A Biography. Volume II, Part 1: 1886-1900 | English | December 1, 2001 |
| Mark Twain: A Biography. Volume II, Part 2: 1886-1900 | English | October 4, 2004 |
| Mark Twain: A Biography. Volume III, Part 1: 1900-1907 | English | October 4, 2004 |
| Mark Twain: A Biography. Volume III, Part 2: 1907-1910 | English | October 4, 2004 |
| The Boys' Life of Mark Twain | English | October 4, 2004 |
| Widger's Quotations from the Project Gutenberg Editions of Paine's Writings on Mark Twain | English | January 1, 2003 |