Arthur Schopenhauer - The World as Will and Representation.
Surprisingly readable and insightful, even if you don't buy his metaphysics. Einstein had Schopenhauer's portrait on his wall and considered him a genius.
* Poetry
John Milton - Paradise Lost
Powerful and beautiful writing.
* Fiction
Rabelais - Gargantua and Pantagruel. Funny and a real feast of words (the translation is a work of art in itself)
Thomas Mann - The Magic Mountain. Haunting and moving
Pierre Choderlos de Laclos - Dangerous Liaisons. Scandalous, gripping.
Ivan Turgenev - First Love. A masterclass in writing. Short, sensitive and exquisitely told.
Marcel Proust - In Search of Lost Time. Exceptionally rich and a beautiful study of love. Reading it is like living another life.
PG Wodehouse - the Jeeves series. Hilarious, perfectly frivolous, light and sunny
* Non-fiction
Stuart Russell - Human Compatible: AI and the Problem of Control. Potential bad outcomes from AI and what we might be able to do about them
Noam Chomsky - Necessary Illusions: Thought Control in Democratic Societies. How public discourse is shaped and controlled
Karl Popper - The Open Society and its Enemies. How to work against totalitarianism