Which books should I read to get better at forming and expressing my thoughts more clearly?

English is not my native language, but I live in the US and has only been speaking it for a few years now outside of my family. I noticed that it became very hard to translate images from my head to words in both English and my native language, it causes me real troubles and I want to overcome that. My relative recommended me to read classical books, because they use a more complex language that makes the reading process a good mental exercise.

I haven't been reading any books other than scientific ones since the middle school, so would like to know if that is true and would appreciate if you could give me a list of good books that could help me to get better at constructing thoughts in my head. Thank you.