If, like me, you have pursued higher math mainly outside of college and grad school, driven by curiosity and motivated by the pure beauty of it (and occasionally a bit of utilitarian motivation as well), then you will probably find The Napkin Project by Evan Chen to be a great, very valuable resource. Perhaps you will find your own journey reflected in one of the paths on this map of the land, or perhaps you will be inspired to explore. The book is packed with tons of good examples, and includes several references for further reading.
I also like that the project is hosted on GitHub. Git may not be the best tool for tracking LaTeX, but shouldn’t technical books be like that these days? A living, self-revising organism, an ongoing discussion?