1984 was good, Fahrehheit 451 and Animal Farm were good (Fahrenheit 451 was by someone else, name not coming to me). All 3 political/free speech, really good. CS Lewis is good (not Narnia or that kind of books, his real books). He's a really facinating person, too.
But the most powerful book ever was Tuesdays with Morrie by Mitch Abbom (i think that's how you spell it). If anyone here has read it, you'll agree. If you havn't read it, read it and THEN agree with me.