After reading the first three books and having been a fan since the first, I couldn't wait to get my hands on book 4, Dark Parallel and I was not disappointed! The story deepens with the fantastic plot leading from the other books, and you can not stop reading once you start. The history about the Mayans, the innovative story lines and the lovable characters only make you love the series even more. By far the best in the series, and If you haven't read any of them yet what are you waiting for! Start with Invisible City and I promise you'll love the series from page one.