Lisp languages should be great for embedding into games to implement game logic, instead of more straightforward solutions such as embedding Lua. I've always wanted to explore this for my iOS side-project game, which now uses an event-based system inspired by ReactiveX, implemented in Lua. This works pretty well but is very hard to debug.

The main thing holding me back to try to replace it with something Lisp-like is that I have zero experience in Lisp programming. I know some FP theory (in fact the Lua-based event system lends some concepts from it), but when I try to reason about common subproblems I really have no idea how to map them to something like Lisp. For example how to efficiently implement a message bus with observers that can register themselves, using state-based functions to execute when certain events are received, scheduling events, async/await to suspend processing until some event is received, etc.

Does anyone have pointers to books or websites to learn 'real-world' LISP programming? In other words not yet another introduction that shows the same old forced examples that just show you how to evaluate an expression or use higher-order functions to solve artificial toy problems, but resources that teach you how to be productive in a Lisp language?

There are good references and snippets on the Cookbook: https://lispcookbook.github.io/cl-cookbook/

for libraries, see https://github.com/CodyReichert/awesome-cl (and see the lparallel or lfarm libraries, channels, cl-gserver, the built-in SBCL threading functions, etc)

Also note that CL is not purely functional, you can throw in FP or OOP or iterative code.