“Truly devastating” for some authors but “like finding out my mom is marrying that cool dude next door that I’ve been palling around with” for another, Amazon’s announcement late last week that it was buying the hugely popular reader review site Goodreads has sent shockwaves through the book industry.

The acquisition, terms of which Amazon.com did not reveal, will close in the second quarter of this year. Goodreads, founded in 2007, has more than 16m members, who have added more than four books per second to their “want to read” shelves over the past 90 days, according to Amazon. The internet retailer’s vice president of Kindle content, Russ Grandinetti, said the two sites “share a passion for reinventing reading”.

“Goodreads has helped change how we discover and discuss books and, with Kindle, Amazon has helped expand reading around the world. In addition, both Amazon and Goodreads have helped thousands of authors reach a wider audience and make a better living at their craft. Together we intend to build many new ways to delight readers and authors alike,” said Grandinetti, announcing the buy. Goodreads co-founder Otis Chandler said the deal with Amazon meant “we’re now going to be able to move faster in bringing the Goodreads experience to millions of readers around the world”, adding on his blog that “we have no plans to change the Goodreads experience and Goodreads will continue to be the wonderful community we all cherish”.

But despite Chandler’s reassurances, many readers and authors reacted negatively to the news. American writers’ organisation the Authors’ Guild called the acquisition a “truly devastating act of vertical integration” which meant that “Amazon’s control of online bookselling approaches the insurmountable”. Bestselling legal thriller author Scott Turow, president of the Guild, said it was “a textbook example of how modern internet monopolies can be built”.

“The key is to eliminate or absorb competitors before they pose a serious threat,” said Turow. “With its 16 million subscribers, Goodreads could easily have become a competing online bookseller, or played a role in directing buyers to a site other than Amazon. Instead, Amazon has scuttled that potential and also squelched what was fast becoming the go-to venue for online reviews, attracting far more attention than Amazon for those seeking independent assessment and discussion of books. As those in advertising have long known, the key to driving sales is controlling information.”

Turow was joined in his concerns by members of Goodreads, many of whom expressed their fears about what the deal would mean on Chandler’s blog. “I have to admit I’m not entirely thrilled by this development,” wrote one of the more level-headed commenters. “As a general rule I like Amazon, but unless they take an entirely 100% hands-off attitude toward Goodreads I find it hard to believe this will be in the best interest for the readers. There are simply too many ways they can interfere with the neutral Goodreads experience and/or try to profit from the strictly volunteer efforts of Goodreads users.”

But not all authors were against the move. Hugh Howey, author of the smash hit dystopian thriller Wool – which took off after he self-published it via Amazon – said it was “like finding out my mom is marrying that cool dude next door that I’ve been palling around with”. While Howey predicted “a lot of hand-wringing over the acquisition”, he said there were “so many ways this can be good for all involved. I’m still trying to think of a way it could suck.”

“Right now, I spend a lot of time on both sites in both capacities,” said Howey. “My guess is that we won’t see many changes at all. I’m betting that the real acquisition here is all the data behind the scenes. The algorithms that tell me what to buy (and almost always nail it) are going to get better. The social networks that feed my reading habit are going to get stronger. The people who helped make Goodreads awesome are going to get richer. And the people at Amazon, who I have gotten to know this past year and who to a man and woman love the fuck out of some books, are going to keep trying to get the right ones in the hands of readers.”

The acquisition of Goodreads follows Amazon’s purchase of Shelfari, another social reading site, in 2008.