Remember door-to-door encyclopedia sales? We do (barely). The transformation of books and the way we read has been swift and remarkable thanks to the Internet, and the idea of buying 26 World Books in monthly installments seems absurd in an age of free Wikipedia. (Not to mention the obsolescence of the venerable dictionary, which began collecting dust with the advent of spellcheck.) And it's not just reference texts that are left ignored on shelves or propping up iffy furniture the world over. More and more people are reading ebooks, with sales of electronic editions besting hardcovers for the first time this summer. The iPad is set to further challenge the physical book's 600-year reign.