What I've read recently [mostly notes for myself to remember these books later]:
Rex Zero and the End of the World, Tim Wynne-Jones [grades 5-8, ages 9-12]
a fifties Cold War kids in suburbia book, from the perspective of a new-to-the-neighborhood kid. A mystery "monster" is terrorizing kids and making them spend their summer in fear and solving the great mystery, at home the news is making their parents build bomb shelters or not talk about things. Some good kids get it and parents don't stuff, some good sibling it's ok to be friends but you don't have to be as long as you can get along and see your siblings as people stuff.
Babymouse, Queen of the World! [grades 4-6, ages 4-8]
fun, silly and not-so-silly graphic novel. Babymouse wants popularity over friends to start, but figures it out before the end. lots of great fairy tale and classic story references (cinderella, frankenstein)
Artemis Fowl the graphic novel [ages 9-12]
I haven't read this series yet, but the graphic novel makes me want to. Evil 12-year-old genius as the central character? Awesome. Not sure my long term patience for the high-tech fairy world, but we'll see.
Amulet, Kazu Kibuishi - Book 1, The Stonekeeper [ages 8-12]
brilliant illustrations, a story painfully similar to Spyderwick Chronicles, but still alluring - mom eaten by blobby thing in basement other world, kids rescue her with the help of the amulet. Cliff hanger.
The Time Travelers, Book 1 in The Gideon Trilogy, Linda Buckley-Archer [grades 5-8, ages 9-12]
Two modern kids that barely know each other get thrust back in time due to an experimental machine. They land in 1763, a time where the details of life (clothes and getting around) are very different, but so are cultural things like the criminal justice system. Engaging, with a riveting story that provides continuous reasons to keep reading till the end.