I'm a fan of The True Meaning of Smekday, by Adam Rex, which happens to be 2007 Cybils winner for Fantasy & Science Fiction Winner for Elementary/Middle Grade children. It's a buddy road-trip story that has alien invasions (two of them!), plenty of illustrations, a Boov-modified hovercar, a brutally humorous indictment of Manifest Destiny, and... what, you want more reasons? Here are 10 more.
Even though it's been around for awhile, I still laugh over the Boov training video for humans to adjust to life after the invasion. You can see it here. Good news! Humans now only have three months to remember instead of those confusing twelve.
P.S. Sam Riddleburger, have you read this book yet? I think the book just bellows your name.