I just finished Maria V. Snyder's Glass/Opal Cowan series (Storm Glass, Sea Glass and Spy Glass). It was compelling and included just the right amount of "cameos" for the Study Series characters. All of the major players were included (save perhaps the Commander, who was only mentioned) but did not dominate scenes or events in the book. They were used appropriately as supporting cast. It was great to see those characters alive again without turning the series into Study, Part 2.
I only have one chief complaint, which has nothing to do with the writing, just an issue I had with a relationship between characters in the book. I won't espouse on that now, as it would be a spoiler. Suffice it to say, it's a sort of Team Edward vs. Team Jacob kind of thing. But, beyond that, the message is a poor one sort of like saying vampires are OK to date, but something more rational and real world that should mean someone is undateable. But I digress.
Snyder again fleshed out her characters well and made me read all three books in the span of a few days (much like when I read the Study series). It's a beautifully-written modern fantasy series and Snyder's Inside Out is in my ereader to be accessed in the very near future.