Animal Farm, Brave New World, The Wizard Of OZ, Aesop Fables, The Odyssey, Alice Adventures Into Wonderland, Fahrenheit 451, Peter Pan, To Kill A Mockingbird, We The Living, Phantom Toll Booth, One Flew Over The Cuckoo's Nest, Pulp,Through The Looking Glass, The Communist Manifesto, Siddhartha, The Old Man And The Sea, Gulliver's Travels, Mein Kampf, The Republic, and Meno.
Several of these books are dystopian novels: Animal Farm, Brave New World, Fahrenheit 451, and We The Living, all of which fit into a general theme of novels which deal with social themes, including The Wizard Of OZ, To Kill A Mockingbird, One Flew Over The Cuckoo's Nest, and Gulliver's Travels.
Of course, there are a few texts that should be of immediate interest: Mein Kampf, The Republic, and The Communist Manifesto. Plato's Republic influenced both Nazism and Communism, and it is likely that Loughner read The Republic as primarily a political piece (rather than as a model of the soul). Many people have expressed surprise that he lists Mein Kampf and The Communist Manifesto. I'm not in the least bit surprised, as both national socialism and international socialism are both, well, socialism, and are both collectivist ideologies. So he seems consistent in his support for collectivism.
What seems to have many people confused is his obsession with grammar, and his claim that the government is engaging in mind control through grammar. I'm not going to argue that he's not crazy for believing this, especially with as far as he seems to have taken it, but at the same time, this in fact reflects some ideas developed by some very not-crazy people -- one being George Orwell (who is, of course, the author of Animal Farm, which he listed). Orwell of course argued that one has to be careful because our thoughts can be controlled through the manipulation of language. Nietzsche (who deals directly with the issue of grammar), the Nazi philosopher Martin Heidegger and the leftist linguist George Lakoff each argued the same thing -- but the latter two at least are very much in favor of such manipulations. I won't pretend that Loughner read Nietzsche, Heidegger or Lakoff -- though Lakoff's ideas on this is widely available through his Huffington Post articles, such as his one on framing. I only mention them to point out that such ideas are not entirely crazy, or even uncommonly held. Further, they may be more coherent than most people know or understand. I see a consistent interest in collectivism, dystopian ideas, and the manipulation of people (consistent with his interests in collectivism, the themes of dystopian literature, and his thoughts on grammar/language). People want him to be crazy because it is too frightening to think that he actually may not be. Of course, this articleciting his postings makes the argument that he is crazy. And perhaps he is (though the author of the article is wrong about the incoherence of the books selected, as observed above). The stuff he rambles on about on years makes no sense, but rest sounds like the kinds of arguments I read from altogether too many of my Freshman composition students. I wish I were exaggerating when I say that.