John C. Nicolay, who had known Lincoln in Springfield, Illinois, served as chief White House secretary from 1861 to 1865. Trained as a journalist, Nicolay had hoped to write a campaign biography of Lincoln in 1860, a desire that was thwarted when an obscure young writer named William Dean Howells got the job. Years later, however, Nicolay fulfilled his ambition; with John Hay, he spent the years from 1872 to 1890 writing a monumental ten-volume biography...