Marginal revolution has an article on the 'books that influenced the me most'. There is a follow up article of others lists here.
No one in these lists seems to mention the Bible. And few the Odyssey and Iliad. Aesop and the brothers Grimm also seem to be ignored. Hansel and Gretel, Rapunzel, little red riding hood, Cinderella, Sleeping Beauty, Snow White, Rumpelstiltskin all come from one book. They are pretty much ubiquitious in the lives of children of my age even if they did not read the original.
Is it naive to think that these stories we heard as children probably influence our thinking far more than books read after our teenage years?
I seriously doubt there are many westeners who don't consider the three little pigs as a moral lesson more often than those from anarchy the state and utopia.
The most embarassing book most of the list writers will admit to is something by Ayn Rand which they now disown. But why is Atlas Shrugged allowable on the road to where they are but Rip Van Winkle and the works of Hans Christian Andersen's are ignored?
By most influential do we mean the book your willing to admit to that you think about while debating people? Rather than the ones that are so ingrained in our lives that they serve as a backbone to how society operates.