As an author, I, too, want others to read my work. To do that, relationships must to be created in order for my books to be found and sold. Joining websites, forums and blogs are a great way to do that. (Easier said than done in many cases)
Of course, Goodreads is a wonderful network, if not the best that I've found. Are there others that you can tell about?
If your book is fiction or non-fiction it will require marketing a completely different group of friends from someone who has just designed a CNC (computerize numeric controlled)device and wanting to market it.
Share with me your advise to others. What works...what does not. This can really help many authors save money and put their effort where it counts.