Publishers Weekly is reporting this in an article today.
Interviews with several major trade houses found all acknowledging that they were selling at least as many e-books as hardcovers through Amazon with one major publisher reporting that in the last couple of weeks the ratio had been higher than the 143 e-books to 100 hardcovers Amazon reported for the second quarter. “[E-book] sales are growing week by week,” this publisher said. … And another publisher noted that Amazon’s e-book sales are not only for titles sold through the Kindle, but for all devices for which apps are available, including Apple’s family of reading devices