I Had a Hippopotamus ($14.95; May 1996; 32 pp.; 1-880000-28-8): A boy opens a box of animal galletas, or crackers, and gives away the creatures one by one: an elephant to a baby brother, a kangaroo to a grandmother. In Lee's first book, polished illustrations with the look of woodcuts allow readers to see that, in the boy's imagination, he is not giving away mere crackers, but real animals, with funny results. The clues to what's real and what's imagined require--and reward- -careful scrutiny. (Picture book. 4-8) . . .