I recently had a chance to read the first book in the "Our Young Guardians" series, Seven & Two. This book really does well with evoking a somewhat mysterious air right off the bat, with limited cover notes and a story that is intriguing right from the introduction.
The book is well written in a way that incorporates a lot of different life lessons into an engaging, fantastical story: relationships, conflict, family, discrimination, good vs. evil, and independence vs. reliance. The children in the story are self-sufficient, forced in many ways to grow up before they're ready, but providing an exciting way for kids to imagine being in charge and making serious decisions while in the safe space of literature.
It's the kind of story that both my daughter and I really enjoy - strong characters, a mesmerizing plot, and a desire to read more of the story after the book is done.