According to The Boston Globe,
The John F. Kennedy Presidential Library and Museum said it will display, as part of a weeklong celebration of Presidents’ Day, a 1930 biography of Abraham Lincoln that was apparently borrowed by Kennedy, or a member of his staff, when he was serving in the Senate in the 1950s.
The Library of Congress book, “A. Lincoln” by Ross F. Lockridge, was found in Kennedy’s pre-presidential papers. It has been listed as missing in the Library of Congress online catalog, and will be returned to its collection after the display.
And from that book, through the magic that is the Internet:
“One day a man who was migrating to the West drove up in front of my store with a wagon which contained his family and household plunder. He asked me if I would buy an old barrel for which he had no room in his wagon, and which he said contained nothing of special value. I did not want it, but to oblige him I bought and paid him. I think, half a dollar for it. Without further examination I put it away in the store, and forgot all about it. Some time after, in overhauling things, I came upon the barrel, and emptying it upon the floor to see what it contained, I found at the bottom of the rubbish a complete edition of Blackstone’s Commentaries. I began to read those famous works, and I had plenty of time; for during the long summer days, when the farmers were busy with their crops, my customers were few and far between.
“The more I read the more intensely interested I became. Never in my whole life was my mind so thoroughly absorbed. I read until I devoured them.”
From A. Lincoln by Ross F. Lockridge, World Book Company, New York, 1930, p. 110