Amazon.com sells TV Guide's weekly magazine for 20 dollars a year, including both the print magazine and a digital copy you can read on Amazon's Kindle app. Most grocery and drug stores also sell TV Guide magazines in the checkout lanes.
To locate back issues of TV Guide, check out sites like eBay, yard sales or a local used book store. Look for back issues being sold in bulk for the best deal. Also, keep in mind that with free TV listings now available online, the modern TV Guide magazine only includes prime time listings and mostly consists of news and commentary on current television shows.