Turns out that the familiar bearded figure responsible for the spine-tingling eloquence of the Second Inaugural Address wrote these chilling-in-a-different-way verses years earlier: “Yes! I’ve resolved the deed to do,/And this the place to do it:/This heart I’ll rush a dagger through/Though I in hell should rue it.” Abraham Lincoln coped with depression, major and chronic, his entire life, contends scholar Joshua Wolf Shenk in his new Lincoln’s Melancholy (Houghton Mifflin), and Lincoln’s struggles with that disease prepared him, the son of an illiterate frontiersman, to lead the nation through its darkest days. The purported link between mental illness and genius puzzled experts long before the advent of psychopharmacology and the birth of Freud, and it remains a potent talking point: Would Lincoln have accomplished more on Zoloft? At the same time, the public’s curiosity about the personal lives of civics class greats has reached muckraking proportions: John Adams was a deadbeat husband; Thomas Jefferson fathered children with his slaves; Lincoln may have been homosexual. Former first lady and mental health advocate Rosalynn Carter appears with Shenk in this discussion of how the 16th president’s melancholy may have kept the union together even as the man was falling apart.