Rex And Lilly Schooltime (32 pp.; $12.95; Apr. 1997; 0-316-10920- 7): Three short, funny chapters comprise this easy-to-read book starring dinosaurs Rex and Lilly from dino-experts Brown and Brown (When Dinosaurs Die, 1996, etc.). Rex faces show-and-tell and trading lunches, and Lilly deals with a know-it-all who tries to answer for her while she is laboriously sounding out a word. Using lots of picture clues and a limited vocabulary, the Browns carry newly independent readers along to a surprise twist at the end of each chapter, painlessly expanding their reading skills in the process. (Fiction. 5-7)