There is a good talk here, a series of talks. Clojure and Rich and the thinking of the entire Cognitect team (Fogus included, of course) have been so influential- intellectually- and many of its and his and their tenets have become mainstream, even dogma. That being concerned about "immutability" is a practice these days is at least partly due to Rich. Can you imagine programming without immutability?

But a big part of Clojure's story has not just been in the ideas, but also in the details of the design and implementation. From the performance guarantees of the persistent data structure implementation, to the idioms around parameter ordering, both of which I was appreciating yet again earlier today- aside from the ideas, there are ergonomics that only make themselves known through use, like easter eggs.

So there is much to mine in tracing through the history of the implementation, revealing those easter eggs in nascent form.