That's a requirement for a test I'm going to take. I tend to learn better with well designed, reasonably comprehensive books that don't treat me like a dumbass (not as a genius either!).

Please notice that I'm not asking for websites, interactive platforms, videos, or whatever, but about books, preferably ones that I can study on my Kindle (so PDFs are not ideal). I know all the major websites but I just can't follow them.

I can pay very small amounts but I'm pretty much unemployed in a third world country so free is always better.

If there are requirements to understand such books, kindly inform!

I finished school more than 20 years ago and I was not a good student. But I'm kind of a decent learner now that I have a diagnostics (ADHD).

Thanks a bunch!

EDIT: guys, I am actually a beginner in the sense that I literally know little to nothing about the subject! I'm also not a math wizard. Advanced suggestions are appreciated but also entirely useless. This is also for a test, so, beyond a very brief introduction, general understandings on the Neil DeGrasse Tyson level is also of little use for me. I don't need to understand the beauty of the cosmos, I need to pass a test. Thanks!