I dont like clojure
"It's Maps All the Day Down"
Spend a lot of time, just learning how you (CRUD) map contents.
There will be enough time to tackle the other cases/tech (atoms, protocols etc) but until you get good at maps don't get bogged down by the other cool stuff.
In reality - its actually Trees all the way down. But, because you don't have proper structures in Clojure, one uses Maps when one should actually be using Trees.