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!

I'm interested in the subject, but don't know where to begin investigating it. I tried to look over the code for SeDuMi, but it is much more massive than I had realized. I have a background in mathematics, if anyone can point me towards a textbook.

This is something weird to me. I think skin color is pretty diverse no matter where you go, or at least, I don't know enough to say otherwise. But take hair color. Europe has more diversity in hair color than almost anywhere else. Same with eye color. Why is this? Is it just because I interact with more people of European heritage on day to day business, or has Europe actually had more mutations which affect hair color, eye color, etc? Or is it that Europe, being a crossroads has had more people immigrate through it.

If this is racist, it's unintentional, this is just an observation, which I've been unable to find an answer to.

If you have an answer, a link to a paper would be great.

Edit: A point against what I just wrote that I thought of: Asia has both mono and double eyelids, which is something Europe doesn't have. Native americans don't count either for or against, since they immigrated fairly late in a small group, which also explains why almost all native americans are type O