Surprised it's not mentioned yet -> "The Alchemist" by Paulo Coelho.
This book is pure gold, however one has to approach it with a right mindset. It's not the best literature, per se, you will ever read, but if you take a deeper look, it's very simple, yet very profound. It somehow reminds me of the quote from Charlie Munger (Warren Buffett long time associate, and one of the wisest man alive) - "Take a simple idea, and take it seriously"