INTERACTION

Thanks Shaun, I wasn't brave enough to check.

Quoting and summarising Alison Flood on the Guardian website

Amazon.com's announced earlier this week that its ebook sales have overtaken hardbacks,.... that, over the past three months, for every 100 hardback books Amazon sold in the US it sold 143 Kindle ebooks.
George Walkley, head of digital at the UK's biggest publisher, Hachette UK, said they saw "terrific ebook sales" at "over five times the sales in the comparable period last year. On frontlist and bestsellers, digital accounts for more than 8% of overall volume," Stephenie Meyer, Michael Connelly, Patricia Cornwell, Martina Cole, Lisa Gardner and Stephen King were the firm's bestselling ebook authors. Walkley put the growth down to a wider range of ebooks being available, a greater proportion of titles being published simultaneously in print and ebook, and the larger range of ebook devices on offer.
Waterstone's said last month that it was approaching 1m ebook downloads from its site, waterstones.com.