Things Fall Appart - because it helped me understand how religions like Christianity and other initially subversive beliefs spread, and the sudden impact of Western culture on other cultures.
Anthropology (Marvin Harris) - because it impacted the way I look at humanity, society and history, and also helped me understand that marxism is much more than an arguably failed political doctrine.
The Bernstein Tapes about Critique of Pure Reason - I am still working through this, but has already impacted my conception of what knowledge is
History of Western Philosophy (Bertrand Russel) - because it made me understand the interwining between ideas and history. A desert island book
Concepts Techniques Models of Computer Programming - still working through it, because ir is making me realize I had no clue about programming and design. Best programming book I have come across
The Prince (Maquiavelli) - because it completely changed the way I look at politics and society
The Making of The Atomic Bomb - because it is a great way to see the incremental progress of science, and made me realize how much those at the leading edge extract from a few crumbles of information. Also the starkest description of the impact of industrialized killing in WW1,