Here are a couple lists of mathematics topics, organized be level, with suggested books for each topic/level. The second one has pretty extensive commentary on each of the books.

"How to Become a Pure Mathematician (or Statistician)" [1]

"Chicago undergraduate mathematics bibliography" [2]

[1] https://hbpms.blogspot.com/

[2] https://www.ocf.berkeley.edu/~abhishek/chicmath.htm