Its the easiest way I have found to keep track of all of my book comings and goings.
All of your books are categorized first into: "currently-reading", "to-read" or "read". Then beyond that you can make your own bookshelves to further categorize them like "cookbooks", "non-fiction" or whatever.
I love the bookshelves because though I am generally a somewhat organized person, I try to be very organized about my books. Some of my bookshelves are:
-on-deck: the next books I will be reading
-batters circle: the books that I'll order from the library once I'm reading my "on deck" books. (Yes, I have since been informed that this baseball metaphor doesn't quite work but I like it so who cares?)
-vacation reads: light-hearted fun books that I am saving to read while lounging pool side or waiting in the airport.
The two other great features of Goodreads is the recommendations and the giveaways.
Goodreads will make recommendations based on books that are on each of your shelves. So if you had a whole bookshelf that only had books about cooking and baking they would recommend those kind of books for that shelf. I have found a lot of great books that I never would have found otherwise this way. It's been great when I'm in a reading slump too!
The giveaways are just what they sound like! Publishers that have new books coming out will list them and you can enter to win them.The expectation is that you read it and then rate it and write a review. I have won about 10 in the past 4 years. This doesn't sound like a lot but I only enter for the books that I am genuinely interested in reading.
You can also "friend" other people on Goodreads to see what they are reading and to get recommendations from them. I'm a bit of a voyeur that way, I love to peep in on what others have on their shelves.
It's easy to sign up, just create an account (or use your Facebook or Twitter accounts) and get to stocking your shelves so you can get recommendations! If you need any assistance let me know and I'd be more than happy to get you started!