Because it's estimated that making one Kindle creates 22 times more greenhouse-gas emissions than producing a book, e-readers are eco-disasters.
The more you read, the more it makes sense to curl up with an e-reader. Though producing a single device takes a greater toll than making one book, you can download indefinitely. According to one study, once you read 23 books, the environmental hit of a Kindle is the same as the print version; download more and your e-reader trumps books. Of course, using it requires energy, but its energy-efficient screen needs less juice than most electronics. And downloading a new book takes only a few clicks, while buying a printed book means driving to a bookstore or having it shipped to you.
Unplug your charger when it's not in use so it doesn't suck extra energy. When you upgrade, recycle your e-reader at Amazon or Best Buy.