Perhaps not the most ambitious choice, but one of the most important aspects of sci-fi is the impact that science has on us as humans. This is a brilliantly written but very straightforward examination of that. For a second option, I'd probably go for

Armor, by John Steakley. It's a great launching point.

The book that started it all for me. I disagree with OSC on a lot of things, but this book is a thing of beauty.