So you're sick of paper. Sick of trips to the bookstore. Sick of the weight of a fist-thick textbook in a backpack. Sick of working your laser printer to death for a stack of papers you'll read once and trash (and sick of the guilty feeling you get when you do it). It's time for an e-reader. The once unheard-of category has been exploding recently thanks to the introduction of hot models like Amazon's Kindle, which turned the market upside and whet consumer appetites for a device most of them didn't even know existed. But what can you expect from an e-book reader, what should you look for in one? Here's a primer on the advantages of e-readers, how to buy one, and a few specific models you'll want to check out.