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.
I had a really neat time reading green and blue mars since I took about a year off in between them and my fading memories of the events in the first book really put me in the headspace of the characters in the later books who had also started to forget and to mythologize. I can't think of a better way to have read it! My only complaint is there was not a single female character except maybe for Nadia whose personality didn't boil down to 'boys make me cRazY!'.