Sam Jordison on the Guardian Books Blog meditates on the eco-friendliness of e-books. He mentions a study on the Kindle that estimates a Kindle produces “roughly 168 kg” of carbon dioxide during its lifetime, whereas a single book produces about 7.46 kg—meaning that a Kindle equals about 22.5 books. So once a Kindle has kept someone from buying 23 paper books, the carbon dioxide savings begin. The author of the study also claims that "a physical book purchased by a person driving to the bookstore creates twice the emissions of a book purchased online." She also notes that...