After Abraham Lincoln's assassination in 1865, William H. Herndon began work on a brief, "subjective" biography of his former law partner, but his research turned up such unexpected and often startling information that it became a lifelong obsession. The biography finally published in 1889, Herndon's Lincoln, was a collaboration with Jesse W. Weik in which Herndon provided the materials and Weik did almost all the writing. For this reason, and because so much of what Herndon had to say about Lincoln was not included in the biography, David Donald has observed, "To understand Herndon's own rather peculiar approach to Lincoln biography, one must go back to his letters." An exhaustive collection of what Herndon was told by others about Lincoln was published by Douglas L. Wilson and Rodney O. Davis in Herndon's Informants: Letters, Interviews, and Statements about Abraham Lincoln . In this new volume, Wilson and Davis have produced a comprehensive edition of what Herndon himself wrote about Lincoln in his own letters. Because of Herndon's close association with Lincoln, his intimate acquaintance with his partner's legal and political careers, and because he sought out informants who knew Lincoln and preserved information that might otherwise have been lost, his letters have become an indispensable resource for Lincoln biography. Unfiltered by a collaborator and rendered in Herndon's own distinctive voice, these letters constitute a matchless trove of primary source material. Herndon on Lincoln: Letters is a must for libraries, research institutions, and students of a towering American figure and his times.