You use Lambda Calculus every day when you write code. Do you know how it works? As a programmer, understanding Lambda Calculus can enhance your skills but it is the very definition of academic.

Pure Math

There are no numbers in Lambda Calculus - only functions. These functions are purely representative and it can bend your brain but then... you get it and you start to realize just how fundamental these concepts are. Lambda Calculus is a pure joy to play with, but there is a bit of a learning curve.