Skylight. Assassins Universe

Ragged, hungry, Skye gets abandoned at the door of what looks like a gigantic prison. The Assassins Guild-an impenetrable fortress. Only they let her in. And now, she either joins or escapes. One final test will determine the future-for herself and everyone around her. "'Skylight' takes one of the less likely aspects of fantasy-the Assassins Guild-and not only does a science fiction take on it, but also makes it seem sensible.
.Kristine Kathryn Rusch makes the entire concept work with a story about morality and hard choices."-Tangent Online "Her method for dealing with the problem, and the ultimate solution, left me hoping for another story or six starring Skye as an iconic space-opera wisenheimer which is about as strong an endorsement as I can give 'Skylight.'"-Primary Sources "Kristine Kathryn Rusch has created both a compelling protagonist and an equally compelling setting.
Rusch writes the world in which Skye finds herself as an insular place filled with mystery, revelations appearing slowly and carefully as the reader learns more about Skye, her past, and her present. While 'Skylight' feels as if it could be the first chapter of an ongoing new series it also works well as a stand-alone story."-SF Signal