For those of you who might be interested, as I write more Christian Cole stuff I’ve been writing up an encyclopedia file for it as well. If CC does well enough, maybe I can release it as a companion accessory. These novels, though targeted for the YA audience, has been one of the best things I’ve worked on, as it allows me to create, bend and shape our world to how I (and Christian) sees fit. It’s been fun writing these books, and hopefully one day someone will snag the series and others can enjoy it as much as I do.
Well, for those who like the encyclopedic kind of stuff, here is a quick preview.
Blight Wolves: also known as Fleckwülfen, these wolves are from the shadowy realm which exists between our reality and that of the Wanderers. Blight Wolves are devilishly fast and smart, but locked to the will of their master. They may only be summoned at the behest of a powerful individual. They are able to shape shift slightly, as exhibited when they dislocate their own shoulders to become slightly more human so that they may climb a ladder. Their pack leader is called the Omega, since the Alpha is definitely whoever summoned them. They are able to subsist in our reality for long periods of time, or until their master either dies or dismisses them. Often mistaken for werewolves.
-See Also: Fleckwülfen; Wanderers; Werewolves
The Brute: One of the five Wanderers which exists just outside our reality, the Brute is perhaps the strangest Wanderer in existence. While the other four prefer to see Earth as a smoldering heap in their trophy collection, he would like Earth to put up a good fight before he crushes it. Enjoys directional confrontation, and unlike the rest of the Wanderers, the title of “The Brute” changes frequently as a demon from their reality challenges and defeats the current Brute.
-See Also: Wanderers
I can’t give more without revealing too much of the storyline, but that’s just a taste of what is to come. Hope your week is going well.
Jason Córdova 
Michael did the same thing for ELFY and what he saw of AN ELFY ABROAD and KEISHA’S VOW — that’s why I have an Elfy Lexicon (I didn’t do much of that, though I have figured out how to translate a few things since — he was better at it, though!).
All I know about it is that it takes an immense amount of cogitation and hard work because I’m not the one who set it up; if you’ve set it up yourself and are working from your own notes, it has to be easier. (Michael also set a great deal of notes aside to make the Joey Maverick Universe backdrop. I have all of that, which helps me write the stories. But there’s still room to add, thank goodness, or I’d not have a prayer of finishing anything.)
Anyway, good for you that you’re doing this! And thanks for posting about it. I agree this is a big part of creating a universe, even in an urban fantasy — the stuff you add in must make _sense_ and actually add to the discussion, and it helps to make it consistent because readers get frustrated when it’s not. (Marion Zimmer Bradley was not always consistent with her worldbuilding in the Darkover series due to how many years she wrote it, how many decades, etc. She told people to live with it and of course, being a huge name in SF/F, she got away with it. But very few of us are ever going to have the stature of MZB.)
A friend just told me about how, when he met George RR Martin at a con a few years back, Martin mentioned that the more popular your books get, the more serious people will take them. Those people, Martin went on to say, will find each and every single inconsistency you write so you better keep track.
But the main reason I’m so picky about my notes and errata (and the Lexicon, which is something else inside the errata and is driving me nuts) is because I don’t need to spend all that time explaining to people why I misspelled a city name in one of the books. Of course, I’m only doing this with Christian Cole. I have a timeline for the Corruptor universe and some notes, and a map for Wraithkin. But Christian Cole has everything I could think of.