Very fond memories of Mir Publishers' science and math books growing up in India in the 80s and 90s. I think English translations were freely available in India. My grandfather would buy them for me to encourage my interest in science and math. If I could find physical copies of those books I would buy them in a heartbeat today.

Slight digression: Russian cartoons from that era are also very interesting. One of my favorite short cartoon from that era (I still hum its music involuntarily): Ikarus and the Wise Men [0]

[0] https://www.youtube.com/watch?v=0Yk1mz23YFA