I could definitely see bundling in a 'codex' at the end of the book that gives more details about the world that many readers would not be interested in. That way they can either read it or ignore it without it impacting the story. If it was a multibook series, I would have it with the last book to avoid any 1) any plot related reworkings and 2) revealing any surprises/plot twists prematurely.
Have you thought about a website, do you have one? I think it is a good idea to share certain information with your readers, teasers etc. Maybe part of your codex could be posted there at the right time. It may add to the intrigue. Just a thought.
Okay, here's my two cents worth. The way I world build is to just write the story. The first draft is always crap that get's heavily edited, but it also gives me a good idea of where things are going and what parts of the world need developed. This way I can focus on the areas of said world that need to be developed for the sake of the story. Writing first gives a good baseline for you to see what needs work, this way it can act as a guideline to keep you from overdeveloping. On the other hand excessive development can lead to interesting ideas that might get used at some point. You just have to strike a balance, it's different for everyone.
