I'm learning Clojure on the basis that you should learn something that will change your way of thinking. I've previously stuck to C-family languages, and I work professionally with Java.
To do this I'm working through Clojure for the Brave and True, which has a good balance of whimsy (it's not so dry as other technical books) and exercises vs plain reading material.
I'm planning to build a slack clone using full-stack clojure, since I learn faster if I get stuck in and try something.