Around 1440 the first printed books were made in Europe. The way of printing quickly improved so that large books like the Bible could be made and sold cheaply. It took 300 calf skins or 100 pig skins to print the Bible. The printers then began to print everything that they thought was interesting:- Ancient Greek and Roman writings, poetry, plays, lives of the saints, mathematics textbooks, medical textbooks, Christian stories, erotic stories, books about animals and monsters, advice to princes as to how to rule their people and maps of the world.