You don't need to buy anything.1. Add any eligible textbook [amazon.com]
2. Proceed to checkout and sign up.
If you already have Prime or have done a trial, you may fail to get the trial.
Details [amazon.com]
"Qualify for Amazon Prime free for 3 months when you order any eligible textbook and enjoy the benefits that come with membership.
There's no obligation--cancel anytime before your free trial is over and you will not be charged the $79 annual fee. Offer valid through October 16, 2009"
