It seems that nobody has mentioned George Orwell so far
1984 or Animal Farm sometimes seem to be describing problems we are experiencing now (or might experience in not so distant future), although they were written a few decades ago. I like his Homage to Catalonia too. In it, he recounts his experience from Spanish Civil War (another famous piece about the conflict is Hemingway's For Whom the Bell Tolls).
And I like classics too. One of my favourites is Dante Alighieri and his Divine Comedy with all its mind-blowing imagery, especially in Inferno