I think reading a lot of books is a good way to improve your knowledge, but don't stick to the ones of your own countries, reading fictions, comics, etc. from other parts of the world will naturally introduce you to things that you are not familiar with.

And if you have the curiosity to try and look what it is about (references you missed, names of people and places, concepts being used, etc.), you will expand your understanding and knowledge of different things. Works also with movies and series, of course.

Be curious, always :)