I recently started looking into the source code of clojure compiler. It helped me understand some data structures like bit partitioned tries, red-black trees and persistent collections, but I'm having trouble going beyond these structures and understanding how they fit together. There are a lot of interfaces in the code and almost no documentation explaining what they mean. Hence sometimes, I find myself getting stuck at some tests which might be meaningful to someone familiar with the source. The codebase is really clean btw, but I'm a student and don't know much about language design. And I'm having trouble keeping everything I read in my head. Intellij is of great help for jumping around the codebase but it can only do so much.

Are there any resources describing clojure's internals? I've already looked at the blog series at hyperion.com. What other advice would you give someone diving into a big codebase?