Awesome to see my favourite author here on Hacker News.

May I also humbly recommend:

* Civil Disobedience (1849) - the classic referred to by Gandhi and MLK http://thoreau.eserver.org/civil.html

* A Plea for Captain John Brown (1859) - Thoreau was one of the very, very few to defend Brown attempt to launch a slave rebellion http://thoreau.eserver.org/plea.html

* Walden (1854) - of course - read the first chapter at least ("Economy") for a timeless analysis of what is necessary in life http://thoreau.eserver.org/walden00.html