We just finished reading this series out loud with our daughter. I didn't even know it was referred to as "The Underland Chronicles" until I found this photo on the web. We didn't buy the box set. I've just been calling it the Gregor series.
I've talked about the other books already, but I loved the last one, The Code of Claw. It's one of those series where as you keep going it keeps getting better but you're always worried that the author is going to do something to undermine the whole thing.
You needn't worry. Suzanne Collins knows her way around a good plot! One thing that I didn't love as the series went on was the whole prophecy thing. Some dude 400 years ago or something left these cryptic prophecies that keep kinda sorta coming true, so the last book comes and we know that there's a prophecy in which the main character is supposed to die. Now you just know that she's not going to kill off the main character in the last book but you wonder how she'll pull it off.
My favorite character is Ripred the rat. Briefly: the series is a modern urban take on Alice in Wonderland. Gregor falls into the Underland which is, of course, somewhere under New York City. How his financially strapped family survives in Manhattan is never fully explained, but who cares? Most of the action takes place below ground. There's a fantastic world of human-sized rats, bats, cockroaches, spiders, mice, and other creatures including a kingdom of humans. The humans and bats are allies and more, but there is a war with the rats and the other critters are free agents which the two sides are trying to recruit or kill off.
Ripred works both sides against the middle. He's not fully trusted by either side but seems willing to help the humans when it fits his secret agenda. In the final book he tells Gregor not to worry about the prophecies so much, they've just got to be superstitious nonsense. Gregor is seriously taken aback because Ripred has promoted certain courses of action throughout the series because of the prophecies. This is where Gregor finally gets that Ripred has been using the belief in the prophecies to further his own (still secret!) agenda. But he (Ripred) isn't too Machiavellian about the whole thing. You get the sense that he's basically trying to help both sides not annihilate each other (though it usually seems if it came down to it, he'd side with the rats over the humans).
Yes, there are parallels with other fantasy series. Here's a young boy who has powers he knew nothing about introduced to a magical world in which he is a kind of chosen one, expected to do certain things and often questions his abilities. One big difference is that he has a complete (if somewhat battered) family that take turns coming down with him, even a toddler! I was not too sure about this toddler thing in the first book, but she grew on me and it was all handled very well. It was an interesting twist on the formula.
It's great that Collins wrote this before she went on to do the massively popular Hunger Games series because I have 5th graders that want me to get them those books and I have to tell them that they can read them, but they won't be checking them out of an elementary library any time soon. But! I have this Gregor series! Battles! Blood! Warriors! Death, destruction, fragile alliances! A strong anti-war sentiment in a war-filled series! Children at risk and sometimes the pawns of adults! Sound like another series? So yeah, it's nice to have this for the middle grades (4th and up) which they can read before they graduate to the YA books in middle and high school.
The Code of Claw was dark, scary, and wonderful. It was a more satisfying conclusion to the series than I expected. I recommend it and the entire series highly.