Books. What are books?
What purposes do they serve?
Are they just there for their appealing looks? Or, do they serve a more significant purpose?
If a book could talk, what would it say?
If a book could walk, where would it  go? and what would it do?
If a book could write a book, what would it be about? And more importantly what would it contain?...
If books weren't books, what would they be?
They would be the unknown thief.

(the last part is about the notion of how,      ' books give you knowledge' and it's basically saying if there weren't books...)