I like Goodreads. It's great to find indie books that no one else knows about (I found The Last Falcon through it and thoroughly enjoyed it). They hold competitions where you can win books (although I've yet to win any). It has a large forum with lots of different groups you can join to discuss books and writing. You can get in touch with authors and, if you're an author, you can have a platform to reach readers.
But mostly it has reviews.
I don't know if anybody has done any statistics on Goodreads ratings but I would guess the average would be around 3.8. And also I disagree with a lot of them. Example:
A Great and Terrible Beauty (loved): 3.78
Evernight (hated): 3.66
The difference is small.
Doing a quick search, these are the average ratings for bestselling YA books:
The Hunger Games: 4.4
Harry Potter (1): 4.38
Twilight: 3.56
The Maze Runner: 4.02
Gone: 3.87
Inkheart: 3.83
Uglies: 3.87
These are the average ratings for some indie books:
The Last Falcon (read in one day): 3.67
Switch! The Lost Kingdom of Karibou (gave up): 4.46
Switched: 3.89 (this was a self-published book that became a bestseller and was picked up for traditional publication)
Arrow of the mist (haven't read yet): 4.22
Altors (haven't read yet): 4.25
And not an indie, but not so well known: The Night Circus: 4 - this was very pretty but I hated the plot and the characters.
Another example of differences depending on the version is Stargirl, a book I absolutely loved when I was a teenager: the one book version is rated at 3.76 for book 1 and 3.78 for book 2, but the boxset is rated at 4.05.
Other famous sci-fi/ fantasy books I've read:
Transition (Ian M. Banks): 3.82
The Assassin's Apprentice (Robin Hobb): 4.1 or 4.27 (depending on the version)
The colour of magic: 3.94 or 4.15 (depending on the version)
The Lies of Locke Lamora: 4.27
Now of course, the averages for the famous books are from over 10,000 ratings (sometimes considerably more), whereas for lesser known books it can be from a dozen or up to a few hundreds, so it's not a fair comparison. Also the readership is different: the rater for Ian Banks is not going to be the same person as the rater for Harry Potter - well, unless they're like me.
My point is that the difference in ratings between great books and average books is small, and sometimes null. Books that frustrated me are loved by some, and books I love are hated by others.
What gives me hope is this: people have different tastes.
Not to say that I won't accept feedback - I always (over)think about it. But it helps me get over the fact that not everyone will like my story. Not everyone will like my character and my world.
And that's ok. I only hope that some will.
Now there's loads of other things involved in rating books, so if there's anything you've noticed, please leave a comment. Let's get a discussion going!