I am a big fan of Goodreads.com. It is the best (in my opinion) of the social networks for readers. I have been tracking all of my book reading there for the last three years and built a nice little community.
I love Amazon and I love Goodreads, but I am a bit concerned about this purchase. Amazon already own Shelfari (which I never liked) and a stake in LibraryThing (which I have never tried). If Amazon actually goes through with this purchase, Amazon will own all or part of three of the largest social media sites for readers.
That does not seem like a good idea for readers.