What book changed your mind?

I'm normally a one-book-at-a-time kinda guy, and couldn't get my head around people that would juggle multiple books concurrently.

But right now I've got almost 10 books on the go, and I’m starting to see the appeal. Your brain finds connections between concepts, like Steven Johnson's "collisions of hunches" theory of creativity, and new—hopefully original—ideas start to emerge.

In honour of the power of a good book, today I want to ask “what book changed your mind?” This could be something you read in your formative years that influenced your worldview, or it could be something you’ve read more recently that made you see something in a new light.

I’ll drop mine in later this evening after a little think. Looking forward to reading yours.