So, why use EDN? Rich Hickey gives a good rationale at the link above. But for me it boils down to a few things.
You know how people use Node.js to let them use the same language on the server side and client side of an application? Clojure and Clojurescript serve that same purpose. EDN extends that to representing data. It’s a subset of the Clojure language well adapted to data.
It’s human readable (most programming languages are). And since it’s a smaller version of Clojure, manipulating it is already built into Clojure development tools. Also, parsing it is already built into Clojure/Script. There are no additional libraries to download and figure out.
So, it’s all one big happy family – server, client and data.