This is almost a second series in the Apprentice Adept series. We are no longer following Stile and are now following his and Blue's sons. Phaze and Proton have now been separated, with no contact for 20 years. Until Mach and Bane switch places and most learn to survive in each other worlds and how to get home.
This is a interesting book you suddenly are not following the same people and its been 20 years, but you quickly catch on to what has happened in these 20 years and what has not happened. But most (but not all) of the twists are easy to spot ahead of time.