Rylant (Henry and Mudge and the Sneaky Crackers, 1998, etc.) slips into a sentimental mode for this latest outing of the boy and his dog, as she sends Mudge and Henry and his parents off on a camping trip. Each character is attended to, each personality sketched in a few brief words: Henry's mother is the camping veteran with outdoor savvy; Henry's father doesn't know a tent stake from a marshmallow fork, but he's got a guitar for campfire entertainment; and the principals are their usual ready-for-fun selves. There are sappy moments, e.g., after an evening of star- gazing, Rylant sends the family off to bed with: ``Everyone slept safe and sound and there were no bears, no scares. Just the clean smell of trees . . . and wonderful green dreams.'' With its nice tempo, the story is as toasty as its campfire and swaddled in Stevenson's trusty artwork. (Fiction. 6-8)