How do I buy a book using an iTunes gift card

Read through this article for instructions on how to use the card:

http://support.apple.com/kb/HT1574

Hello Lola1104,

You redeem your iTunes Card.

You install/open iBooks. Then you search the book you want, and you click on the price, and then you click on "Download".

Cedric

Go to the iBooks store and swipe to the bottom of the featured tab and then tap on Redeem in the bottom center row. You will be able to add the gift card in there.