This is such a great series. (Review obviously contains spoilers if you haven't read the first one.) 
 The magical barrier between Quill and Artime has vanished, and the two worlds are allowed to intermingle. In a perfect land this would be ideal, but there is still animosity between the Wanteds and Unwanteds after their battle. Their beloved High Priest is dead, and many Quillians are moving to Artime willingly, leaving Quill in shambles. Alex and Aaron, the twins living on complete opposite ends of the spectrum, find themselves in similar situations in their respective lands--whether willingly or not. 
 Their story is told from both their perspectives, going back and forth between Artime and Quill, and it works wonderfully. Artime is growing rapidly due to its many new residents, yet Quill is struggling to build itself back up. War is imminent, and the tension builds. You wonder who's going to break, and what's going to happen. Because anything can happen when magic is involved. 
 It leaves a lot of questions--someone's a traitor, and who is it, and why? And what's going on in the islands around Quill? And what's with the mysterious, silent children who were washed ashore? Well, that's what the final book is for, I suppose.