The continuing paperback revolution in children's books is doing wonders for parents, schools and libraries that have grown numb over the cost ($4.95 and up) of any hardback books for the young. Led by Dell and Viking, more and more publishers lately have been bringing out durable, attractive and low-priced paper editions of children's classics, new and old. Among the greats, near greats and notables now available:
Mary Poppins, by P.L. Trovers, Harcourt Brace Jovanovich; $1.45.
The Phantom Tollbooth, by Norton Juster, Random House; 95¢.
The Little House books, by Laura Ingalls Wilder, Harper & Row;...