This will be a very short post because I have nothing positive to say about Goodreads, which is an obnoxiously popular website for basics. Goodreads is the kind of thing that exists for that person you know (or knew, or only kinda know) who writes a Facebook update about how they really need a good book to read. This is an example of delicious irony and a demonstration of why I had to stop using Facebook, because the type of person who would put that on Facebook is also the person who probably never reads an actual book.
Thus-- Goodreads. The interface is based entirely around user-created profiles, which allow one to list books read, books being read, or books waiting to be read. Then algorithms generate recommendations for you, and ads from publishers for the latest romance novels are embedded in your recommendations. Ta-da!
I suppose I'm not exactly the target demo because I've never needed a book recommendation in my life; I have quite the opposite problem, which is why 25% of the books on my shelves haven't been read yet. But even so, I tried using it with an open-mind, and I found the recommendations to be incredibly generic and unsophisticated, and in general the whole tone was low-brow. Lots of recommendations for John Green books, etc.
I would recommend skipping Goodreads altogether; if you want to socialize about a shared interest in books, join or start a book club. If you want sophisticated book recommendations based on what you've already enjoyed, visit a local library or an independent bookstore. Also, if you're not boycotting Amazon, they have user profiles and recommendations and socializing and basically everything you can get from Goodreads, but also HBO and free shipping.