“Yeah, it’s kind of second-grade, I know, but once the word poop has been said fifty times, the fifty-first time is twice as funny. Try it.” Demonstrating his narrator’s insight, conceptually at least, Riddleburger sends three normally unadventurous young friends on a surreptitious (and, as you might guess, foredoomed) expedition to their small town’s sewage treatment plant. Intrigued by a newspaper article’s reference to the antiquated plant’s open-air “sludge fountain,” Lyle, Marilla and Dave decide that they must see for themselves. The goopy geyser turns out to be every bit as disgusting and fascinating as they’d hoped (Lyle later writes a haiku about it), and they get a far closer look than planned when Marilla drops her new camera into the settling pool. The author presents the tale in a mix of standard type and a legible hand-printed font on lined paper, with the odd line drawing or photo added. He takes up too much space filling in backstory, but the trio’s “adventure” is credibly worked out, engagingly related and, unsurprisingly, likely to be greeted with howls of laughter by second-graders of all ages. (Fiction. 7-10)