I had a lot of these books as a kid. I'm not even 100% why, but my dad glommed on to the idea that they were of high quality, and also quite inexpensive. Probably my favorite was "Higher Mathematics for Beginners" by Yakov Zeldovich[1]. I was a voracious reader, and largely taught myself calculus from it. Another one on probability and statistics I also found quite accessible (can't find it immediately).
There were some other sketchier pop-sci books, I remember one that had the "water has structural memory" theory in it. But likely those didn't do any lasting damage.
FYI - There is a later version of the above book titled "Higher Math for Beginners" (with Yaglom) and "Elements of Applied Mathematics" (with Myskis) - https://mirtitles.org/?s=zeldovich
Hard copy versions are available from Aargon Press on Amazon India.
There were some other sketchier pop-sci books, I remember one that had the "water has structural memory" theory in it. But likely those didn't do any lasting damage.
[1]: https://mirtitles.org/2022/07/04/higher-mathematics-for-begi...