Fear and Trembling - Kierkegaard
Methusela's Children - Heinlein
The Origin of Consciousness in the Breakdown of the Bicameral Mind - Jaynes
The Structure of Scientific Revolutions - Kuhn
The Illuminatus (Trilogy) - Shea and Wilson
5 Books
I think there's two questions here - what books did it for you and what books do you recommend.
Like Alice In Wonderland and Through The Looking Glass was huge for me as a kid in how I turned out but I don't think it did anything for my politics. Refusing to be a Man by John Stoltenberg was also huge for me, but I don't know that it was all in good ways. The Grounding of the Metaphysics of Morals by Immanuel Kant was a big deal for me too but I don't know that I'd recommend it.
These ones were a big deal for me and I recommend them -
Peoples History of the United States by Howard Zinn
Reading Capital Politically by Harry Cleaver
Capital and the 1844 Manuscripts both by Marx (I initially read the stuff that's in the Marx Engels Reader)
The Ignorant Schoolmaster by Jacques Ranciere
Handmaids Tale - Margaret Atwood
Brother in the Land- Robert Swindells
The Sea, The sea- Iris Murdoch
Huckleberry Finn- Mark Twain
Value Price and Profit- Karl Marx
But what most started to form my political views was reading ''An essay on the principle of population'' by malthus and realising how wrong it was.
Good idea for a thread. I started a similar ones ages ago, but now can't find it.
For me it'd be:
War and Peace - not the actual story but the historical essay running throughout, about history being made by the sum actions of millions of people, not great leaders. This pretty much totally changed my view of society and how it works.
Communist Manifesto - confirmed me being a socialist
1984 - I'm pretty sure contributed strongly to a distrust of the state, although it didn't obviously at the time (we were taught it as an anti-communist book)
ABC of Anarchism - confirmed me being an anarchist
1984 - George Orwell - stopped me from becoming a Marxist
The Disspossed - Ursula le guin - Portrayed a fictional anarchist society in stagnation. Showed how an anarchist society might function, highly recommended.
The God Delusion - Richard dawkins - Confirmed me as an atheist.
Understanding Power - Noam chomsky - Was my first introduction to radical ideas.
Animal farm - George orwell
I, Robot - Isaac Asimov (Asimov pretty much got me into Science Fiction...and Science in general).
A Solitary Blue - Cynthia Voigt (it's a book aimed at young teens about how a kid handles his parents seperating and finally divorcing. I first read it when I was 9 and my parents were being shit and it still speaks to me.)
A People's History Of The USA - Howard Zinn (gave me lots to discuss with my American friends 
)
Nineteen Eighty Four - George Orwell (helped me gravitate towards anti-state left politics while I was a teenage liberal).
Catch 22 - Jospeh Heller
Two books that I read at around the same time that had quite an influece on me were:
What a beautiful Sunday! by Jorge Semprun
and
The Russian Enigma by Ante Ciliga
Thy are both connected in a way as they both talk about the experence of communists in the camps. Reading them both at the same time gave me an insight into the differences, and similarities in the experience of CP members in the camps in Stalinist Russia, and Soviet Germany.
Devrim
First books that steered me into the direction I've had for most of my life was Alan Sillitoe's Loneliness of the Long Distance Runner and then Papillon by Henri Chariere. Berkman's ABC of Anarchism was influential and the Paz book on Durruti and Arshinov's book on the Makhnovists were both influential.
The Idiot - Dostoevsky
The Clay Machine Gun - Victor Pelevin
Conquest of Bread - Peter Kropotkin
Negative Dialectics - Theodor Adorno, it has changed my life in that I devoted/wasted several years trying to understand it, and it gives off an aura of benevolence that saved my life.
Abnormal - Michel Foucault, although any of his lecture series could be included
and the tao te ching for a giggle
gdid - tragic 
There seems to be a few books that've been said a lot...for me, looking back over the years, my 5 would be:
At High School, Catch 22 by Joseph Heller and 1984 by Orwell both helped me formulate the beginnings of a critique of modern capitalist society.
Next, various writings by Nachman Syrkin and Ber Borochov - back when I was a Socialist-Zionist, reading these two trying to resolve the contradictions inherent in Socialist-Zionism and realising I totally disagreed with them on lots of things steered be towards an anti-state, anti-nationalist libertarian socialism, which was confirmed by looking around me (as I was living in Israel/Palestine at the time) and seeing the ultra-nationalism that was there.
And then books and pamphlets like the No Gods No Masters anthology by Daniel Guerin, Anarchism: Arguments For And Against by Albert Meltzer, Mutual Aid by Kropotkin and Nationalism and Culture by Rudolf Rocker helped me develop my anarchism by narrowing down what I agree and disagree with in each 
Woops, thats a few more than 5.
edit: playinghob reccomended a book that I'd forgotten about, but wish I hadn't. The Ragged Trousered Philanthropist by Robert Tressel was another one of the books I read in High School that had a big effect.
guydebordisdead wrote:
Harry Potter and the Philosopher's Stone
Harry Potter and the Prisoner of Azkaban
Harry Potter and the Order of the Phoenix
Harry Potter and the Half-Blood Prince
Harry Potter and the Deathly Hallows
I just got through the deathly hallows in the weekend, not a bad book the ending was a bit sappy and they could have killed off a few more of the lead characters.
Anyway my books would be:
Anarchism and the Black Revolution - Lorenzo Kimboa Ervin
Eon - Greg Bear
Valencia - Michelle Tea
Anarchy - Errico Malatesta translated by Vernon Richards
The Mars Trilogy - Kim Stanley Robinson
Heh, I first read it a while ago at the local anarchist bookshop (which I later ended up doing shifts at )- I thought the arguments against were a bit piss-poor and involved a fair bit of misrepresentation, but the arguments for were decent. Ended up buying a copy last year, as something to lend to a friend that was becoming interested in anarchism. Which reminds me of a good topic to start, I'll do that now.
Fiction :
The Illuminatus Trilogy (Robert Shea and Robert Anton Wilson)* I first read in the mid 1990's.
Non Fiction:
Rules for Radicals (Saul Alinsky )
The Wretched of the Earth (Frantz Fanon)
Propaganda: The Formation of Men's Attitudes. Jacques Ellul
A People's History of the United States (Howard Zinn)* I first read this around 2001
'Planet of Slums' , 'Dead Cities, And Other Tales' , 'City of Quartz: Excavating the Future in Los Angeles' (all by Mike Davis, I read all the shit by him I can get my hands on, by far one of my favorite authors ever.)
(semi?) Theologoical:
Purity of Heart Is to Will One Thing (Søren Kierkegaard)
(To Be a Christian Is) To Be a Revolutionary Padre J. Guadalupe Carney
John Brown (W.E.B. Du Bois)
* = books that finally got the ball rolling in side my head. I would have classified myself of Conservative Capitalist Libertarian as late as 2002 or so.
Earlier today, while reading a book that was recommended to me here on LibCom, in a bout of ADD, I began to analyze the role books have played in my intellectual development. At the end of this 5 second distraction I concluded that, from what I have seen on these forums in the short time I have been a member, books seem to play a major role in all of our lives. With that assumption, I thought up this ingenious thread that begs the question of which 5 books (I know, it's constricting, but nobody will pay attention to the limit after a few posts, so it doesn't matter much) really shaped who you are. This is important not only to get a feel for the LibCom members we see posting from day to day, but also as an informal checklist of books for our own individual intellectual development.
I am aware there is a LibCom reading list of sorts, but this thread intends to be a bit more personal.