What did one book say to another?
I just wanted to see if we were on the same page.
What do you call a person whose library books are overdue?
A bookkeeper.
What did one math book say to the other math book?
Do you want to hear my problems?
What do you do when a dragon bites your library book?
Take the words right out of his mouth.
Who writes invisible books?
A ghost writer.
Knock knock
Who's there?
Cardigan
Cardigan who?
Oh, no! I went to the library and forgot my card again.
Jokes courtesy of http://librarykvpattom.wordpress.com/category/library-jokes-cartoons/