
Fill in any gaps in your knowledge with this overview of key topics in undergraduate mathematics, now with four new chapters.
https://www.cambridge.org/core/books/all-the-math-you-missed...
Good alternatives are The Princeton Companion to Mathematics by Gowers and Mathematics: Its content, Methods and Meaning by Alekxandrov, Kolmogorov, et al. Those present much more detailed maps so YMMV.
* For an introduction (and a reference) to various areas of Modern Mathematics that one didn't even know existed, The Princeton Companion to Mathematics and The Princeton Companion to Applied Mathematics are a must.
* All the Math You Missed: (But Need to Know for Graduate School) by Thomas Garrity - A survey and a good adjunct to a textbook.
* Mathematics: Its Content, Methods and Meaning by Kolmogorov et al. - Classic text from the great Russian Mathematicians.
* Methods of Mathematics Applied to Calculus, Probability, and Statistics by Richard Hamming - Unique text from the great Richard Hamming (also checkout his other books).
There is plenty more of course, specifically; checkout "Dover Publications" texts, many of which are classics and affordable.
Also, timbuktu manuscripts - showed a history that I had never really heard of. These are written manuscripts of african scholars which are hundreds of years old, and still exist today. Some record the history of great west african civilizations along with other things they studied (e.g. science, religion, math, literature, ect). I was never taught this history even existed but yet was made to learn the various details about asian, european, middle eastern, central/south american history. This, and the attempts to destroy/steal these manuscripts at various points in history, made it click how serious power of controlling information, and ultimately influencing beliefs can be, with respect to giving legitimacy to the various rulers/authorities. Beliefs/perceptions matter quite a lot. This 1hr lecture is quite good: https://m.youtube.com/watch?v=lQiqyyRfL2Y&t=16s
Behavioral biology class from Dr. Sapolsky (Sanford) - explains a lot of why we behave the way we do, from different biological perspectives https://m.youtube.com/playlist?list=PLqeYp3nxIYpF7dW7qK8OvLs...
Garrity's "All the Math You Missed". Brings you up to speed fast, and has great references.