I picked up the first book of this series (The Wind Singer) off the library shelf because I thought the cover looked cool. I was very surprised when I liked it as much as I did. Normally, when a book is that good, I do not go on to read the entire series, because often the first book is the best and it is down hill from there. I went ahead and broke that line of thought because I enjoyed the first one so much, and checked out Slaves of the Mastery from my library. I couldn't believe it: it was BETTER than the first book. That's never happened to me before. I have now bought the entire series and am reading through them again.
I think that certain parts of this book could be a little scary for youngsters, because William Nicholson addresses all kinds of social issues (and not pretty social issues, at that), and there a couple battle scenes that are pretty graphic. It is a perfect young adult book, however, and I recommend it above any other young adult fantasy book I have ever read, including Harry Potter, and the Sabriel series (which was one of those series where the first book was REALLY good and the last two kept getting worse). In fact, there were parts that had me laughing out loud (the boy, Bowman, is very clever sometimes. The cat had me cracking up, too), and there were parts that brought me to the brink of tears. It is a hard call between this one and The Wind Singer for which is my favorite of the trilogy.