From the Super Mario Wiki
Johannes Gensfleisch zur Laden zum Gutenberg, known in-game as simply Johann Gutenberg, was a German inventor whose innovations contributed significantly to the widespread use of the printing press. As the son of a wealthy merchant, he had the opportunity to experiment until the printer was able to print simple poems in 1450. After a court case against Johann Fust resulting in his unfortunate loss, he was close to penniless, though a later title of recognition granted him a stipend until his death in 1468. In Mario's Time Machine, Mario meets Gutenberg in 1455 after traveling back in time to Mainz to return a Metal Type needed for his printing press.
According to Mario's Time Machine, Johann Gutenberg grew up in Germany dreaming of a way to quickly and easily produce books ever since he was a kid, as scribes needed to create copies of every text by hand. As he inherited a large sum of money, he was able to dedicate his life to finding a method of doing this, which he eventually concluded is possible by printing words in a way that makes copying effortless. He first attempted to use wood, but the letters came out too blurry to be read. He spent thirty years and all of his inheritance to perfect the printing machine, and at last printed his first books in 1455, the Gutenberg Bibles.
Mario's Time Machine
In Mainz circa 1455, Johann Gutenberg is in his workshop, fussing over his strict schedule for completing the printing machine. When Mario time travels to Mainz, he does not know that Gutenberg is the person who needs the Metal Type; as a result, if Mario attempts to talk to him, Gutenberg tells him to leave him alone, as he is too focused on the printing press. Gutenberg's Metal Type can only be returned to him after talking to the other inhabitants of Mainz, all of whom know about Gutenberg's history and plans, and absolutely confirming that the Metal Type belongs to him. Once this is done, Mario can return to his workshop and bring back his Metal Type. Gutenberg is overjoyed to have it, and says that with this final piece, his masterpiece is now complete. Mario then asks him what he is going to do next, and Gutenberg replies that he needs to catch up on his reading list, as he has not read anything for the past thirty years.