*Contains Mild Spoilers*
All the positive reviews of this series are spot on, but I would throw out one caution to parents who are trying to decide allow this series for their children. The violence level in the books is about on par with the Harry Potter books (which I've allowed my son to read), but the ending lacked emotional resolution. Basically, Gregor returns from the "wars" the equivalent of a wounded veteran, suffering from what appears to be PTSD, and is left with an uncertain future.
On the one hand, it is a much more realistic than your typical fantasy novel, and I have to give the author credit for not glamourizing war. On the other hand, it left my then 8-year old son sobbing and ultimately very unsatisfied with the series. It's always been hard to find appropriate books for him, since he reads above his grade level, and I did read the first one all the way through before letting him read this series. Just wish I had jumped to the end - I would have held off on this a couple of years until his emotional maturity caught up with his reading skills.