Why are so many people happy about Johannes Gutenberg's invention?
Johannes Gutenberg, as I assume you know, was most famous for having invented the printing press. Because of his invention, books became more and more affordable. Before he invented the printing press, all books were hand copied and only a very few people could afford any book at all. After Gutenberg, books and other printed things became so much more affordable that just about anyone could have access to at least some of them.
Historically, this has made many people happy. Now everyone can have their own Bible and everyone can have their own copy of the works of Shakespeare. Just about anyone can have access to whatever kind of printed stuff they enjoy. If you think about the hype over the Harry Potter series, you can see just how many people are made happy by such things.
Gutenberg's invention of the printing press holds significance for many reasons. Spreading of the word through printing helped to increase both literacy and spirituality. The ability to print text helped to spread the word of Christianity, for no longer did it solely have to be passed by oral tradition. Additionally, the advent of the printing press helped to enhance literacy and the ability to read and write throughout Europe and then in the New World via the Age of Exploration. Gutenberg's invention introduced an entirely new medium into the discourse and helped to transform societies both within Europe and outside of it.