Amazon is offering 3 months of free Amazon Prime trial membership for adding to cart one eligible textbook. You don’t need to buy this. Please note that this is not valid for existing or previous prime members.
- Add one book to cart
- Proceed all the way to checkout, and click “FREE Two-Day Shipping with a Free Trial of Amazon Prime” option
- Confirm your free 3-month trial
- Go to “Manage My Prime Membership” and disable auto upgrade.
Note, you do not need to purchase a textbook to get the trial.
The Markr 
If you have a Prime membership, you may want to check out http://www.guaranteedprime.com. It is very user friendly, and provides accurate, Prime Only results.