Prime will cost you $79/ year or $6.58/ month. This is what you get:
- Lending Library -- 1 book/ month
- Prime Instant Videos -- unlimited viewing / selection smaller than Netflix
- "free" 2-day shipping -- for eligible items / no minimum purchase
Which of those services will you use and is it worth $79/ year? Keep in mind that without Prime, free Super Saver Shipping requires a $25 minimum purchase. Otherwise, you'll either have to save up small orders or pay upwards of $5+ for standard shipping (3-5 business days); and even more for expedited shipping. I've had non-Prime free shipping orders take close to two weeks to reach me; and I live in Amazon's hometown.
So it comes down to how often you buy from Amazon, and if the eligible book and video selections are worth it to you.