Goodreads is only the latest, according to ebookfriendly.com
Since 1998, when Amazon acquired BookSurge, along with Custom Flix and Mobipocket, the wallet has been ever-open, and the sphere of dominance ever-widening.
And this infographic, created by Meet the Boss, isn't even up-to-date -- it was created in July 2009.
You can check out the official Amazon record of business deals and takeovers, but be warned that it is a very long page.
With thanks to Jacqueline Church Simonds