These are sites designed for book readers to track what they've read, what they'd like to read, and to help readers find the next book to read. They're social networks and communities build around books and reading.
Booklikes is the "newcomer." Founded in 2013, it's a bit different in that it's built around blogging about the books you read, on a blog hosted on the Booklikes.com site. As they say, "BookLikes helps people share their reading life and discover new books. It's a blog platform designed for book lovers." You can use it just to track your own reading, but there are also community-driven challenges, group reads, and discussions. You can set up an "author profile," too. There's a useful FAQ about the site. Accounts are free.
Goodreads Goodreads is the largest of the sites; it's wholly owned by Amazon.com. You can track and review books, and read reviews by lots of other readers. There are discussion groups, book giveaways, and it's probably the site that most author-friendly in terms of promoting your own books, though they're dead serious about their community standards, and there's a fair amount of politicking via reviews. There's an iOS and an Android app that can convert photos of ISBN barcodes to an entry in your "shelves" of books. There are group reads, challenges and discussion groups too. Accounts are free. There's an About Goodreads page. There's a field on your AW profile where you can enter your Goodreads profile link if you want.
LibraryThing is serious about the library aspect of its services. LibraryThing does a great job of making it easy to catalog books and review them, and is a rich source of conversations about books. A basic account is free and allows you to catalog 250 of your books, as well as full access to the site. A lifetime account is $25.00. There are privacy controls, so that you can make your profile and reading lists entirely private, partly private or public. Amazon has a small (very small) investment in an otherwise privately held site. They offer book giveaways. They have an iOS app, and sell a CueCat bar code scanner that lets you scan and automatically catalog your books based on the book's ISBN barcode. You can read their About page, and a blog post about what makes LibraryThing LibraryThing. There's an iOS app that you can use to photograph and catalog books based on the ISBN barcode. There's a field on your AW profile where you can enter a link to your LibraryThing profile if you want.