You're getting pictures of food because yum!
When you go to Goodreads to look at a book, I'm almost positive you pay attention to the aggregate rating for that book because aggregate ratings tend to be a more accurate predictor of whether a book is good than any single rating. This, at least, is the reason why I pay quite a lot of attention to that little number right under the title of a book.
Now, for me at least, the sweet spot for that number tends to be anything 4.01 and above (I think the highest I've seen is 4.53 given the criteria which follow). This applies only when the book has 100+ ratings, has also already been published, and is within genres that I enjoy. Basically, books that fit these criteria have a much higher chance of me enjoying them. Books which fall between 3.80 and 4.01 tend to be hit or miss, and anything below that has a pretty high probability that I won't like the book.
I'm a pretty jaded reader as far as readers go as evidenced by my Goodreads account - my average rating for all books is 2.96, and I've read and rated 1430 of them. As such, my standards for ratings is pretty stringent so the difference between good and bad is very narrow. Perhaps you guys also have a system when checking out books on Goodreads which is similar to mine but with slightly different numbers.
Now I crave cookies
In order to actually get a good aggregate estimate, I have found that you need quite a few ratings in order for some sort of consensus to arise. On Goodreads at least, this number seems to be 100 although the higher the number, the better the aggregate estimate is in general (in statistics they would say 30, but I've found 30 to be very much inadequate).
This is important because publishers tend to target pretty specifically reviewers who will like the book. Obviously, this is to the publishers' benefit because they want good reviews for the book when it comes out in order to boost sales. Thus, I tend take high numbers pre-publication and even for the first couple months post publication with a grain of salt.
Granted, I realize that I am sort of shooting my own foot since I am a reviewer of books, but hear me out. As a reader, this is where the individual reviews of the book become very important early on. Because you can't trust the aggregate numbers as much, it is important for a reader to find reviewers who have similar reading tastes. If you know that when a reviewer likes something, you will like it and ALSO that when they dislike something, you will dislike it (a good percentage of the time), then you should (perhaps again obviously) pay particular attention to that reviewer.
These pictures have helped to keep your attention
Erm... because if I don't like the genre to begin with it really doesn't matter how good the book seems to be, I'm probably not going to like it. I will admit that there have been some cases where a book with a lot of general buzz will be to my liking even though it doesn't fall into sci-fi and fantasy although I'm not sure I've ever met a pure horror book which I've liked.
P.S. Despite the silliness of the photos, I hope the article itself was interesting ^.^