So, what's a star worth? I throw them out there pretty flippantly. It's time for some consistency in my ratings.
I think this feels right:
5 stars = Awesome! I'm going to read you again!
I loved your characters--in fact I'm still thinking about them right now! I loved your story--I couldn't put you down! I loved your writing--your author has some serious talent! You didn't just entertained me, you moved me! I could relate to you! I'm going to be actively campaigning to get as many people as possible to read you--starting with my own children! Thank you for the pleasure of reading you!
4 Stars = Awesome! But once is enough.
Your characters and your story are still bouncing around my brain. You didn't move me, but you did entertain me. You are definitely going on my list of books to recommend, but I probably won't share you unless someone asks.
3 Stars = Good try.
You entertained me, but there were some problems. I'm having trouble remembering some of your characters names. Reading you was a positive experience, but I don't think I remember exactly why. Your writing might have gotten in the way of your story, or you might have crossed some moral lines around language, sex, or violence. I'll tell people about you when they ask, but I'll probably have a "but" attached to my recommendation.
2 Stars = Lame.
I don't hate you, but I didn't enjoy reading you either. You had promise, and in the hands of a more capable author you probably would have done much better. Your writing ruined your story. I didn't like your characters--either they were immoral or they were boring. Because of you I'll probably think twice before I read anything else by your author.
1 Star = Complete Fail.
I will actively campaign against you and your author. If I had it my way no one else would ever read you again. I gave you my time, and you took it, giving nothing in return. You are lazy. You are immoral. You are stupid and you assume I'm stupid too. There is no forgiveness for the offense you have given me.