Scrumptious Dessert?

So, remember a couple of weeks ago I wrote a review of People of Sparks and how I felt like City of Ember was just an appetizer for People of Sparks and I was wondering if the last book,  The Diamond of Darkhold, would be a scrumptious dessert. Well, I finished The Diamond of Darkhold, and it tasted more like a Hostess Twinkie than tiramisu. 


The Diamond of Darkhold is the final chapter in the story of Lina and Doon, two residents of the former city of Ember, current residents of the village of Sparks, the surviving remnant of a civilization that annihilated itself through greed and violence.  The story picks up during the first winter that the former residents of Ember are living in Sparks.  After living their whole lives underground, the Emberites were unprepared for the cold, rainy weather of above-ground winter.  Lina and Doon decide to return to their former home to try and find something to help their new neighbors get through the long winter months.  They find hints in an old book that the people who built their city may have left something behind, and they set out to find it.

It's not that I didn't enjoy the book, because I did (after all, Twinkies are a tasty snack!).  I just found there to be the same general lack of substance in this book as in the first, City of Ember.  The story was enjoyable, the characters were well-written, the setting was evocative-there just weren't enough universal themes for me to sink my teeth into.  People of Sparks had so much to say about the way that we as a society view outsiders, or the way people use fear to manipulate others, or the way that we solve (or fail to solve) conflicts. Diamond of Darkhold was entertaining, but ultimately it didn't really speak to any larger truths.  I realize that I read lots of things for entertainment only-I certainly don't expect existential enlightenment from a cozy mystery or formula thriller.  However, if a young adult novel is going to really grab me, given the readability level, it has to have something more to say.