I'm reading Science Fair, by Dave Barry and Ridley Pearson, to the 5th graders at school. It's got a lot of age-appropriate suspense, including spies from Krpshtskan (pronounced just like it looks) who have an actual viable plan for bringing down the USA. Also car chases, with the protagonists driving the Oscar Meyer Wienermobile.
It gives me a chance to use a pretty good Russian/East European accent, which the kids seem to enjoy. It also features characters called Darth Vader and The Wookie, and a light-saber battle broken up by Princess Leia and an actual demonstration of a Jedi Knight's use of The Force.