1. Dumas Malone's six-volume biography of Thomas Jefferson.
2. Patrick O'Brian's astonishing Aubrey/Maturin series of novels (first one is Master and Commander). I have found no other writer who takes such joy in language. And the protagonists, while not Objectivist heroes, are admirably rational Men of the Enlightenment.
3. Great fun: Bill Bryson's earlier books, including The Mother Tongue, The Lost Continent, Neither Here Nor There, Notes from a Small Island.