The Bible was not his first product; that would have been too ambitious and even controversial. The first book to come out of his shop, about 1450, is presumed to be the Donatus Latin Grammar, a book with a proven market.
As with good software, functionality comes first; beauty is a feature.
Just as today we debate the roles of Twitter and Facebook in the Arab Spring, so do scholars still argue over the press' role as tool or catalyst.
Books changed even how we learned and remembered. Scholars no longer had to travel to books; now books traveled to them.