A year ago, Amazon raised its free two day shipping minimum to $49 for non-Prime members . This weekend, the company decided to drop the price back down to $35 . That threshold applies to shoppers who are not Prime members, and the minimum for free shipping on books remains $25 . While Prime users already get free shipping on their orders, non-members now only have to spend $35 at a minimum in order to get free shipping on eligible items. The minimum order for books has remained the same at $25. Amazon appears to be working to compete with traditional retailers looking to muscle their way into the online retail space. Last month, Walmart introduced free two day shipping on orders $35 and over, while Best Buy introduced its own $35, two day free shipping for its members last July. It's all part of an apparent battle for online shoppers who have yet to join Prime . An estimated 44 percent of US households subscribe to Prime, making them far more likely to sho...