Crime and Punishment. Anna Karanina. ANY Tolstoy or Dostoyevsky. Classics are classics for a reason - because they're THAT profound and well written.

A little known book that I read that was mind blowing is Leaves From a Russian Diary, which is a first hand account of the horror that was the October Bolshevik revolution. It's jaw dropping and I cried.

My favorite writer is Kafka because his writings were mind bending! From the Metamorphosis, written from the perspective of a beetle, to The Burrow, written from the perspective a burrowing animal, to The Trial, about a man charged and on trial for something the state will never tell him what it is, he was master of the surreal and very funny, too.