The very first book that
Gutenberg/
Johann Gutenberg printed was an
edition of the
bible now known as the
Gutenberg bible. It is very
famous in much the same way as the
Penny Black is very famous for being the first
postage stamp. It was the first and thus a
model for
everything that came later.
The Gutenberg bible is not extraordinarily rare, it is, however, useful as a popular tool for promoting libraries and archives due to its fame. It was typeset in such a way that it could illuminated by hand. The intellectual content of the Gutenberg bible approaches zero cost, since books with equivalent content/identical content are now mass produced by many commercial and religious printers.