Brenna Skirata Currently, a stand alone. When I was at an author signing, Holly Black was asked if there would be more. She said she doesn't know yet. If there is another story that she feels she can write, then she will.
Gillian Dawson I'm just reading Cruel Prince, and a number of the characters from this show up in a crowd scene. Same giant world of faerie, but this one is a stand alone.
Sarah Stand alone, but there's a major reference towards the end to her earlier novels (Tithe, Valient, Ironside) that indicates they're all in the same world, so it might be worth it to read those if you get the chance.