I am opening an exception for goodreads, I sometimes click compare books and OMG they read a lot of the same obscure stuff I did also, and there is a special category of real friendship which is liking the same books and being able to talk about them.

What you read that and love it also? You also hated that? That might not be real friendship but it is a kind of friendship for some specifically rare viewpoints...

If you actually chat with them on regular basis (not just like each other's posts or whatever you probably meant), then they absolutely are.