The Bible is the first hand-written bound.
Just because God can not be seen, he made sure that we can learn about him by written words.

Thousend of years ago he choose man to be his "messengers". They were to pass-on the message in written word on paper.

God inspired these people by his invisible spirit.

Bron: http://www.real-life.nl/waarom/bijbel_bestseller.html