What books should i read to understand rationality, romantic and enlightened views on reason, etc?

The best way to do it is to work your way through civilizations. Start with Greek, that's where it all began. Thales of Miletus, Socrates, Plato, Aristotle. Then move to Romans, and then go to the early Christian philosophers. This will give you the best basis so that you can move forward to the newer philosophical works.