Netflix uses a software algorithm to recommend movies and Zappos uses one to recommend shoes. Now Goodreads, the social network for book lovers, is introducing an algorithm to recommend books.

Goodreads was started in 2006 for people who wanted to talk about books online. Its 4.6 million members load their virtual bookshelves with books they’ve read, are reading and want to read, rate and review them, and discuss them with friends and others on the site.

On Thursday, Goodreads will announce that it has acquired another start-up, Discovereads.com. It uses machine learning algorithms to analyze which books people might like, based on books they’ve liked in the past and books that people with similar tastes have liked.

Otis Chandler, Goodreads’s founder and chief executive, says the site has been an online version of walking into a friend’s living room and scanning the bookshelves to get recommendations. But readers need more than that, he said, particularly now that libraries, bookstores and some newspapers’ book review sections are disappearing and e-bookstores are inspiring more self-published authors.

“This will give the casual reader a quick answer to ‘What should I read first?'” he said. Once people have rated 10 books on a scale of five stars, Goodreads will be able to suggest books they might like.

Determining people’s tastes is a lucrative business, as Netflix has demonstrated by giving $1 million to the first team to develop a better movie recommendation system than the one it was using.

For books, Amazon.com already has a robust recommendation system. But Mr. Chandler said Goodreads’s recommendations will be better because Amazon considers books a customer has browsed or bought, so buying a gift for a child could throw off the recommendations, for instance.

Goodreads will also use the recommendations to help authors and publishers advertise their books to readers who are most likely to be interested in them. Seventeen thousand authors, including James Patterson and Margaret Atwood, use Goodreads to advertise.

In addition to advertising, Goodreads, which has raised $2 million from investors including True Ventures, makes a small amount of money from commissions when someone clicks from its site to an online bookstore to buy a book.