Fiction

The Trial (Kafka)
The Grapes of Wrath (Steinbeck)
One Day in the Life of Ivan Denisovich (Solzhenitsyn)
The Golden Compass (Pullman)
A House for Mr Biswas (Naipaul)
23 Tales (Tolstoy)
Crime & Punishment (Dostoevsky)

Non-fiction

The Book of Why (Pearl)
Shackleton's Boat Journey (Worsley)
The Years of Lyndon Johnson (Caro)
Free to Choose (Friedman)
Capitalism & Freedom (Friedman)
The Age of Reason (Paine)
The Ultimate Resource II (Julian Simon)
Beyond Good and Evil (Nietzsche)
Philosophical Investigations (Wittgenstein)

Math

An Introduction to the Theory of Numbers (Hardy & Wright)
Matching theory (Lovasz)
Combinatorial Problems & Exercises (Lovasz)
The Structure and Interpretation of Computer Programs (Abelson & Sussman)
Linear Programming (Chvatal)

Books that are at the top of my "to read" pile

On Growth and Form (Thompson)
Feynman's Lectures on Physics
The Nature of the Chemical Bond (Pauling)
The Science of Mechanics (Mach)