No way I could avoid this topic.
From the side of a philosphy / english (the language, not literature):
well my first suggestion would obviously be
Hobbes's Leviathan
Stephen Pinker is a great author and I recommend
Blank Slate and
Stuff of Thought Locke - because while his writings are terrible, he has some good ideas
Hume - because there is a skeptic in all of us
Mills - because utilitarianism is important
Kant - Because he is the greatest philosopher of all time
Rawls - because he is the modern day champion of social contract theory
Hauser's Moral Minds was also a good read
Bioethics: An Anthology is a great compilation of applied ethics in the world.
I strongly suggest you read the
three page article by Edumnd Gettier called the Gettier problem as it is one of the most important philosphical works in the past 50 years.
my wife also says I have to add
Camus... because existentialism matters...
We also could not live without the
The Cambridge Dictionary of Philosophy
The OED is a great resource and one day my bookshelf will be lined with the entire thing.
The best grammar text book I have ever used and should be sitting right next to any writing aide you own would be
Understanding English Grammar
Another good resource book is the
Origins of the English Language
Other books, without links since you have probably either heard of them or read them already:
Darwin's The Origins of Species
Hawking's Brief History of Time
Chomsky's Language and Problems of Knowledge
Friedman's The World is Flat