A flock of hippos runs the emotional gamut from morose to mirthful in this offering from one of children’s literature’s most prolific authors. An appropriately rhyming text carries amusing illustrations of gray, lumpy hippos in a variety of postures that reflect the mood in question. Emotions are conceptually tough for toddlers, marking this effort for children in the older end of the range, for which its complexity is just right. One of three hippo books from this duo out this month.