McBratney (Guess How Much I Love You) introduces a joey named Little Roo who is ""feeling grumpy and he didn't know why""-and, as all mothers know, nonspecific malaise is the hardest to dispatch. Everything Little Roo's mom does to cajole a smile out of her son-a tickle, a toss in the air (for which the book's orientation momentarily turns vertical), a game of hide and seek-fails. But when mom, with her joey tucked into her pocket, mistakenly bounces into a mud hole (""slippity... slippity... slide and... slop!"") and gets ""soaking wet and slimy from the tops of her ears to the tips of her toes,"" Little Roo finds himself grinning from ear to ear (even though he's mud-soaked, too)-because, as all kids know, there's nothing funnier than a grownup with her dignity askew. Fuge's (Sometimes I Like to Curl Up in a Ball) kangaroos are wonderfully expressive: when Roo's mother is finally at wit's end, she grasps her recalcitrant offspring firmly under the shoulders and regards him nose-to-nose with sourness worthy of the Grinch. McBratney convincingly conveys a youngster having a bad day, but the narrative unfortunately is not as spare here as in his previous works. Instead it spells out every iota of the action (""She gathered up some dry leaves, tossed them into the air and all the leaves came down on Little Roo""). Ages 2-6.