Goodreads is a classic, and for good reason. A simple, unfussy design makes it easy to use. It has helpful tools to track books you’re reading and books you want to read, plus a rating system to rank and review your books and find options similar to ones you enjoyed.
There’s also a social element, where you can friend other readers and even authors. Goodreads allows you to set up reading challenges, too, so you can push yourself to read a certain number of books per year.