- Regular dead-tree books.  Can be used or new, not too fussy about that.

Broken down by (sometimes rough) topic to help with finding them:

Biology/natural history:
Douglas Adams - Last Chance to See
Carl Zimmer - The Tangled Bank
Carl Zimmer - Parasite Rex
Sean Carroll - Endless Forms Most Beautiful
Sean Carroll - Making Of The Fittest
Matt Ridley - Genome: The Autobiography Of A Species In 23 Chapters
Matt Ridley - The Red Queen: Sex And The Evolution Of Human Nature
Matt Ridley - The Rational Optimist: How Prosperity Evolves
Nick Lane - Power, Sex, Suicide: Mitochondria and the Meaning of Life
David Quammen - The Song of the Dodo: Island Biogeography in an Age of Extinction
Dr. Tatiana's Sex Advice to All Creation: The Definitive Guide to the Evolutionary Biology of Sex
Susan McCarthy - Becoming A Tiger
Richard Dawkins - The Blind Watchmaker
Horace Freeland Judson - The Eighth Day of Creation
J. A. Baker - The Peregrine


Physics:
Smolin - Life of the Cosmos
Smolin - Three Roads to Quantum Gravity
Steven Weinberg - The First Three Minutes
Steven Weinberg - Dreams of a Final Theory: The Scientist’s Search for the Ultimate Laws of Nature
Lawrence Krauss - Fear of Physics
Neil DeGrasse Tyson - Origins: Fourteen Billion Years of Cosmic Evolution
Neil DeGrasse Tyson - The Sky Is Not the Limit: Adventures of an Urban Astrophysicist
James Kakalios - The Amazing Story of Quantum Mechanics: A Math-Free Exploration of the Science that Made Our World
Brian Cox & Jeff Forshaw - Why Does E=mc^2? (And Why Should We Care?)
Richard Feynman - QED: The Strange Theory of Light and Matter
Richard Feynman - The Character of Physical Law
Sean Carroll - From Eternity to Here: The Quest for the Ultimate Theory of Time
Brian Greene - The Elegant Universe
David Deutsch - The Fabric of Reality
David Deutsch - The Beginning of Infinity
Lockwood - The Labyrinth of Time
Danny Bonaduce - Random Acts of Badness: My Story
Simon Singh’s - Big Bang
Leon Lederman and Dick Teresi - The God Particle: If the Universe is the Answer, What is the Question?




Philosophy:
Douglas Hofstadter - Godel, Escher, Bach: An Eternal Golden Braid
Daniel Dennett - Consciousness Explained
Daniel Dennett - Sweet Dreams: Philosophical Obstacles to a Science of Consciousness
Zoltan Torey - The Crucible of Consciousness
A.C. Grayling - What is Good?: The Search for the Best Way to Live
A.C. Grayling - Thinking of Answers: Questions in the Philosophy of Everyday Life
Mark Balaguer - Free Will as an Open Scientific Problem




Psychology/neuroscience:
VS Ramachadran - The Tell-Tale Brain
Philip Zimbardo - The Lucifer Effect
Stanley Milgram - Obedience to Authority
Christopher Chabris - The Invisible Gorilla



Other nonfiction:
Jared Diamond - Guns, Germs and Steel
Jared Diamond - The Rise and Fall of the Third Chimpanze
Ian Kershaw - Fateful Choices: Ten Decisions that Changed the World, 1940-1941
Steve Spangler - Naked Eggs and Flying Potatoes: Unforgettable Experiments That Make Science Fun
Simon Singh - Trick Or Treatment?
Charles Freeman - The Greek Achievement: The Foundation of the Western World
David Crystal - The Stories of English
Thomas Gilovich - How We Know What Isn't So: The Fallibility of Human Reason in Everyday Life



Discworld books by Terry Pratchett:
The Colour of Magic
The Light Fantastic
Equal Rites
Mort
Reaper Man
Guards! Guards!
Men At Arms