This book courses off from the study series with a new protagonist Opal. Opal is in the Study series having a little role in the first book and a somewhat larger role in the last book in the series. All the old characters from the Study series is in this one as well, except for Valek. You kind of need to read the Study Series to understand this book better since it reference back to that book a lot.
Opal is a glass maker, actually a glass magician she can do a lot of nifty treat with glass that she learns along the way in the book. The protagonist in both Study series and this glass series have a lot in common. People are trying to kill them, they learn new tricks with there magic, find a lover, and everything ends up okay in the end. It isn't very different than the study series. Same things are going on in a way. This one seemed to have a little bit more imagination in what was going on with her. And all in all was a good sister book to the study series.