The invention of the printing press by Johannes Gutenberg around 1440 revolutionized the spread of knowledge. Before this invention, books were copied by hand, a slow and expensive process. The printing press made it possible to produce books much faster and cheaper, leading to a significant increase in literacy and the sharing of ideas across Europe. This era is often referred to as the 'Gutenberg Revolution'. What was the main effect of the printing press, according to the text?
A) It made books more expensive.