I've just seen the amazing exhibition of the 3,700-volume library of John Adams, entitled "John Adams Unbound," at the Boston Public Library, and I strongly recommend it to those interested in the mind of one of the four top thinkers of the American revolutionary period and the making of the new nation, along with Jefferson, Hamilton, and Madison (not to slight Franklin). Aside from historic interest, the exhibition is a pleasure for lovers of books. Not only are many of the books, displayed open in glass cases, beautiful things as books, but most of them show Adams's own notes on what he is reading, penned in the margins.
Lean over a book that describes Blenheim Palace in England, and you see a note in brown ink, "Mr. Jefferson and I visited here in 1786." Under a drawing of an ancient Egyptian procession in honor of the goddess Isis is the grumpy comment, "Is this religion? Good God!" In his copy of Mary Wollstonecraft's "History and Moral View of the Origins and Progress of the French Revolution," he argues with the famous protofeminist on virtually every page, and you can almost hear him fulminating at her excuses for the excesses of the revolutionaries.
If you're visiting Boston, I would suggest you skip the pricey salons of Copley Place and Newbury Street and spend a half-hour with old John instead. It's free.