Didn't see the ending coming, though I probably should have. (I've been slow because I don't read well on my phone, not because of the book itself.)
The trio of cheery - grumpy - angsty worked well, I thought, especially since you took care not to lock them into the roles. Bella is my favourite character; she reminds me of someone but I genuinely can't figure out who she's pinging as.
There's two moments which jumped out at me as drawable: the fence-jump in chapter 8, which I might attempt, and the Gloam beast appearing during Terry's spell, which I think is beyond me.
Fanfic... not sure. I tend to play with minor characters, and I'm not sure there's anyone who falls in the space between "too major a player" and "No distinguishing features". I'm also wary about writing anything which will be proven wrong by the next book. :) I'm most interested in the wizards from a fanfic perspective, because they're the ones who stand apart from other depictions of the same concept.
One possibility would be a crossover; the Gloam has Mist-like properties which would make something Percy Jacksony work, but it might be more fun to run some or all of the trio into Dresdenverse or Night Watch vampires or werewolves. Actually you push a lot of the same buttons as Night Watch and its sequels, apart from not being Russian and dark. So that could have potential.
When I asked about your fanfic policy, what I meant was: if it gets written, do you want to see it, and if so, any restrictions on what you see? I'm thinking of the Marion Zimmer Bradley fanfic incident, and don't want to make you uncomfortable.
hS
(Of course for real funsies I would contrive a reason for Selene to run into them, with or without Kaitlyn in tow... :D)