Malaysian here. I learned mostly from AD&D books back in the day. They used more complex words, and the books were more about storytelling than rules back then. I guess you can call it a "technical" book if you stretch the word enough. Writing helped too, mainly arguing with people on the internet. I got an English score of 34 for the ACT, which is apparently in the top 1% in the US.

Another interesting thing was when someone posted a tool that would fingerprint you based on your usage of words on HN. Apparently mine matched with many others; there seems to be a kind of self-learned foreign writer dialect, which I thought was interesting. There's a tendency to translate from your native language as well. Like I know "I got..." is a bit odd, but it's not grammatically incorrect and it clicks with my thought patterns better, so it sticks.