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.
The second book in the series (The Dark Forest) is by far my favourite of the three. Builds on the world of the first in a way that's so satisfying, has some great characters, and a truly fantastic ending. The third is a bit more hit or miss, but still worth reading to close it out. But man, The Dark Forest is just so so awesome.