Non-Fiction
How to Read a Book
Mortimer J. Adler
What you don't learn in high school English class. All of those prefaces, introductions, and such mean something.
How to Read Literature Like a Professor - Thomas Foster
The symbolism and subtext in writing. What they try to teach you in high school English that you don't really believe.
The Effective Executive
Peter Drucker
The stuff Drucker wrote 50 years ago as cutting edge thinking has transformed into the platitudes of today. Too bad few really demonstrate what he espouses. This is on the difference between Effective and Efficient. Foundational reading for his other work.
A Short History of Nearly Everything
Bill Bryson
It's not often that a science book can make you laugh out loud. I highly recommend this as an audiobook.