That decade spans my high school and undergraduate education. I list the following twelve books because they provoked strong intellectual or aesthetic engagement and, in some cases, long-term agreement.
Aristotle, Nicomachean Ethics
James Herriot, All Creatures Great and Small
Alistair MacLean, The Guns of Navarone
Ludwig von Mises, Socialism
Friedrich Nietzsche, Genealogy of Morals
L.M. Montgomery, Anne of Green Gables
David Nevin, Dream West
Ayn Rand, The Fountainhead
Mary Renault, The Persian Boy
Edmond Rostand, Cyrano de Bergerac
Thornton Wilder, The Ides of March
Taylor Caldwell, Captains and the Kings
(The standout book from my earlier years was Elliott Arnold’s White Falcon.)