Great book series...though of the 4 in the Series, this is the most emotionally depressing as Will, our hero, is enslaved and abused near to death before an unlikely rescue.  Book 4 takes the story farther after Will's rescue and recovery and is more "cheery".  In a nutshell...books 1 & 2 were great.  Book 3 will likely be depressing for young Will is a really good kid.  If you buy book 3, be sure to get book 4.