This is the second book in KJ Cartmell's Liam Wren series.  One can learn a lot by reading the books of this remarkable series.

KJ Cartmell's stories are noteworthy for how well he handles a long list of characters, as one would reasonably expect to encounter in a story set in a boarding school.  And these characters are not just names, no, not at all.  Each one is a fully developed personality with his/her own unique style of speaking, acting and pursuing his/her own goals, stemming from both their own innate natures and from the Houses they have been Sorted into.  KJ can give us all lessons in delineating each character with a few broad brush strokes, a few telling events that make him or her stand out as an easily recognizable and remembered individual.

This story, which focuses on a group of five first-year Slytherin girls, opens our eyes to the vast vista of Slytherin House, both physically and functionally.  No longer is our image limited to the Malfoy-Crabbe-Goyle-jerks-criminals purview afforded by the seven canon books.  Here we see the 24-7 scheming, jockeying for position, bragging about oneself, insults to others, every action having a distinct motive, planning one's own moves, analyzing everyone else's moves, leaving nothing to chance....

"That's how things get done in Slytherin House, after all.  You make friends, build alliances, and out-maneuver your enemies..." says one character.

The visual world-building is remarkable also.  The architecture and floor plan of Slytherin House are precise and complicated in KJ's mind's eye, so well described that we can see it fully, the many rooms, stairways, floors, like a miniature city behind the Slytherin front door, a beehive of activity and intrigue, marked by complex politics and governed by elaborate tradition and protocol.

Within this environment, the plot of the story involves the unraveling of a mystery involving the dangerous times of the Second Wizarding War, ten years previously, and the desperate measures taken during that war to protect the non-pureblood wizards and witches who were the targets of Voldemort's reign of terror.

Although this book is the second in the Liam Wren series, it is the first book to delve so deeply into the culture, the ethos and the day-to-day operations of Slytherin House.  I can never think about Slytherin House the same way again, after reading it.