Twisted is currently the most recent published book in this series and it ends on a cliffhanger that opens up even more questions about this C2 / Operation I.Q. mystery. There doesn't seem to be any news about a 6th book just yet and, while a part of me hopes this series will continue, I think I can personally feel satisfied with the answers I received for the questions that had been running around my head since I read Nightmare as a kid.

As it stands, Twisted is a slightly sleeker book than the four that came before it. The writing is just as concise and charming despite the time between publications, though the formatting is different but still easy to read and approximately the same length as the other stories in the series. Overall, it's a great sci-fi spy mystery that I can see a lot of kids creating their own endings to!