Dragon Breath! My DS6 looooved The Dragon Breath series! Good, clean fun. For good measure he also read Diary of a Wimpy Kid, 4 out of 5 Percy Jackson books and the 13 Story Treehouse. Oh, and anything Calvin and Hobbes he can get his hands on. I know it's been said before, but does anyone feel like they have a "Calvin?" My DS identifies with Calvin so closely that he designated one of his favorite stuffed animals to be his version of Hobbes.
Anyway, when I tried to impose my book preferences, he shut down and refused to read at all. So, I'm guiding, and trying to be breezy about the mediocre, slightly too mature kid books.
Right now, he's reading the BFG and we're both happy about it. Roald Dahl seems to hit the sweet spot for adventure and silly.