Skip all the pop science bullshit suggested below. That's almost entirely sugar water, and beyond that; most of it is actually actively wrong.
Read anything written by Ancient Greeks; Aristotle, the Iliad, Herodotus, Plato. There's a reason people still read these dead white guys, and there is a reason that peak times of excellence in Western Civilization have been peak Ancient Greeks. It will make your thinking three dimensional, and give you perspective as to the world you live in today as a software engineer.
Read anything written by Ancient Greeks; Aristotle, the Iliad, Herodotus, Plato. There's a reason people still read these dead white guys, and there is a reason that peak times of excellence in Western Civilization have been peak Ancient Greeks. It will make your thinking three dimensional, and give you perspective as to the world you live in today as a software engineer.