Amazon reported sales of $12.95 billion for the fourth quarter, up 36% from a year ago. But operating income actually declined, even with almost $3.5 billion in extra revenue, down $2 million at $474 million. The company says they sold “millions of third-generation Kindles” in the quarter, and indicates “Kindle books have now overtaken paperback books as the most popular format on Amazon.com” and “this milestone has come even sooner than we expected – and it’s on top of continued growth in paperback sales.” The company adds that, “since the beginning of the year, for every 100 paperback books Amazon […]