We've just discovered the Zac Power books - not sure if these are available in stores in the States though (am in Australia). My boys (5 and nearly 7) are desperate for them. Zac is a 12 year old spy who races through 24 hour missions in between schoolwork and chores. His older brother Leon invents the gadgets for GIB (Government Investigation Bureau). The books have a reasonable number of diagrams of the gadgets (lava skis, robot octopus/submarine, personal hologram projector etc) and take about 45 minutes to read out loud. I find them rather too much like read-aloud cartoons, but this seems to be a positive thing in the minds of small boys.