Beneath the surface of the apparently untutored and deceptively frank Abraham Lincoln ran private tunnels of self-taught study, a restless philosophical curiosity, and a profound grasp of the fundamentals of democracy. Now, in Lincoln: A Very Short Introduction, the award-winning Lincoln authority Allen C. Guelzo offers a penetrating look into the mind of one of our greatest presidents.

If Lincoln was famous for reading aloud from joke books, Guelzo shows that he also plunged deeply into the mainstream of nineteenth-century liberal democratic thought. Guelzo takes us on a...