ADOPTION is cleverly explored in Horace, by Holly Keller (Red Fox, $68). Horace lives happily with his parents. But he is different. He has cheetah spots while the rest of the family have tiger stripes. Despite reassurances of love, he goes off to seek a family where he thinks he will belong. He has a good time, but by evening misses the special care of Mama and Papa, who have come out to find him. This simple story about belonging is lovingly told and illustrated with an array of animals under-fives will enjoy. Dinosaurs Divorce, A Guide For Changing Families, by Laurence Krasny Brown and Marc Brown (Little, Brown, $42), tackles its subject more directly. It spells out in clear language the steps involved and the implications, from when parents start fighting to living with step-parents. This book may help children come to terms with their own confused emotions and reassure them that when all else fails parental love remains constant. But some could find it too explicit. It could also alarm children who have no experience of serious parental discord. Youngsters are likely to appreciate the zany cartoon illustrations of dinosaur families going through divorce more than the harsh realities depicted in the text. In The Night Shimmy by Gwen Strauss and Anthony Browne (Red Fox, $51) many children will identify with shy Eric's imaginary friend and protector who is everything he would like to be in life. The shadowy workings of Eric's imagination are cleverly matched by the use of black pages with white text, which brighten to more regular black on white as the Shimmy gradually disappears with the arrival of Eric's first real friend.