Book Detective

Amazon(.com): the "grand-daddy" of them all, in terms of democratizing the book purchasing process by moving it online; the current "king of the hill".
I have to give them a credit for brilliantly taking advantage of the social aspects of the Internet and creating the first functioning (distributed) mass reviews/feedback system.
Building the platform that allowed people to write reviews, getting them to do this by encouridging them, sharing the reviews (providing free access) and packaging them as a final score is what really made their site popular.
This, plus figuring out the distribution channel and driving down prices.
Recently though, it seems that companies have found way to game the rating system and Amazon cares less and less about books; their book page are becoming cluttered and their rating less and less reliable; their book search is weak (I don't mean the actual item matching).
They became more commercialized and less in touch with the "soul" of the books/reading process. I guess this explains them byuing Goodreads.

Goodreads(.com): more humane, book centric site. Huge user participation. Huge book database and data points for each book. Lots of editorial support (book lists).
One of the best book sites out there.

eBooks.com: an online site dedicated (only) to ebooks - providing virtual content in a virtual world - it's actually quite logical, isn't it?
They offer "a vast number of ebooks in every conceivable subject category", and claim a catalog of more than 1.3 milion books and more than 4 million users.
They were around since year 2000?! I am surprised they are not more popular, maybe being located in Australia has something to do with it.