Two books top my favorite of all time from my collection of non-fictions. Each one is a great read that is worthy of anyone's collection: The Selfish Gene by Richard Dawkins and Guns, Germs and Steel by Jared Diamond. I learned a great deal from these books.
Two of the best Computer Books I ever read are,
The Design of the Unix Operating System by Maurice J. Bach (timeless classic)
C++ for Real Programmers by Jeff Alger (this is NOT your average language book)
Even if you don't need to learn Unix or C++, you can read these books for the sheer intellectual challenge and satisfaction. I got hold of the copy of the Unix book right out of college in 1991, I still treasure it. The C++ book, I incidentally got it from the UNC library for course work, I loved it so much, I bought a copy.
Other books I like from my collection:
The Code Book by Simon Singh
The Origins of Life by John Maynard Smith
Newton's Gift by David Berlinsky
To Infinity and Beyond by Eli Manor
Zero by Paul Seif
First They Killed My Father by Loung Ung
I have this habit of voluntarily lending the books I like to our friends. Luckily most of them return it, even when I loose track. Nowadays, I keep a log :-)