Theories abound as to his life. Some historians speculate that he was a brilliant inventor who died penniless, and others believe he was eventually rewarded by the Archbishop of Mainz and carried on printing until his death.
Paul and Blaise believe that Gutenberg saw his talents as a divine gift, so it wasn't for him to sign his work, there being a more powerful Creator behind it.
Around 1430 Gutenberg left Mainz for Strasbourg where he was involved in a number of activities that show him as a bit of an entrepreneur. He was paid to teach people the art of polishing semi-precious gemstones. He was also in partnership with men who produced tokens to be used during pilgrimage.
Financial and legal records are the only way of tracking Gutenberg. They show that he was part of a group that disputed his father's will around 1420. He drew a form of life insurance payment from the city of Mainz, but there were problems over that, and he was sent into exile for political/economic reasons. There are tax records to show how much he paid for wine in Strasbourg. He was sued by a woman who claimed that he had promised to marry her. But very little is known about his printing press as there are no records. The invention itself did not form part of taxable income, so it does not appear in taxation records.
The most significant record is a court document that records a dispute between Gutenberg and his business partner over the huge amount of money required for his printing press. Another document, dated just after Gutenberg's death in February 1468, is from a powerful citizen who recorded that he was then in possession of type and other equipment left at Gutenberg's death.
Q. Why was the first book printed a Bible?
You may quite legitimately be thinking 'Why not?' In a culture where atheism was virtually inconceivable and Christianity considered to be the only true religion, the Bible seems an obvious choice. But most people, including the clergy, did not own Bibles; their main knowledge of the Bible came from sermons and from extracts used in church services.
Far more common was the 'Book of Hours', a handbook of daily prayers. The size and sumptuous quality of the Bible shows that Gutenberg was making claims for the status of his invention, that it was every bit as prestigious as a lavishly illustrated manuscript. The future of print may have lain in mass production, but Gutenberg did not want to make his mark with something pitched at the mass market. If he had wanted to do that he would have produced a 'Book of Hours'.