It used to get recommended all over Stack Overflow, but I did really love reading Göedel Escher Bach. That book taught me to see math as a game or, equivalently, as purely exercises in shuffling symbols around, with intent.

That shift in outlook really unlocked the fun in math for me. I learned about category theory through Haskell shortly after, and got into number systems and the surreal numbers and quaternions after that. There’s so much neat math out there that the wall of calculus and linear alg really imposes right before all the good stuff.