The fables of Aesop are the only text that has been illustrated so often, so diversely, and so continuously that the history of the printed illustrated book can be shown by them alone. Illustrated Bibles outnumber the fables, but the sacred text imposes a more hieratic and less varied approach. Ovid's Metamorphoses accounts for a great number of illustrated books, but this classical author has suffered many periods of neglect. The fables' combina tion of freedom of approach and constant appeal has kept them steadily popular as a subject for book illustration from the fifteenth century to the present.