Most original, exciting, fresh, mindblowing? Doesn't have to be theory, non-fiction, or even leftist. I just wanna get to know more exciting books.
My own answers:
Non-fiction: Debt - The Last 5000 Years and A Paradise Built In Hell were paradigm shifts for me, in a great way.
Fiction: Gonna have to be The Trojan War Will Not Take Place. Yes it's a play from 1935 but it was more interesting for me than many more current books, and the anti-war message is unfortunately still fresh.
Yeah we're (assuming you're American) all programmed from birth to desire the American dream, so when we see it thoughtfully portrayed our lizard brains are like "yes yes yes qsmmmmmm" despite a deeper understanding of the fact that it's built on the slaughter and misery of millions.