1. Measurement by Paul Lockhart
2. An Infinite Descent into Pure Mathematics by Clive Newstead (available @ https://infinitedescent.xyz/). It taught me basic discrete math and proof writing.
3. Apostol's Calculus Vol 1. It is just so beautiful.
tldr: I discovered math when I discovered a book on writing math proofs by Nancy Rodgers[0]
https://www.google.com/books/edition/Learning_to_Reason/NuN2...