Have hardcover host (or make) a forum that people can discuss, recommend and find books, or to just have a place to talk with people of similar interests.
In the future it can also facilitate things like Q/A's with authors or polls

This can be an extension of Book discussions, where book discussions is creating threads off of a book or author, the forum structure allows for more then just that, by having book threads be under a book category it allows users to create threads unrelated to one specific book, either in the book category or in a separate category. Other features like prompts can also become a type of thread under a prompts category.

The forum structure allows for people to communicate with anyone, either by creating or joining a thread. Sub forums are also an option, say a reading group, where they are separated from the public global forum and can have their own admins.