I have never cared for the 5-star rating system very much. It's too...uncompromising. So here is my system, inspired by Jennie's B(ook)log
10: Perfect. Left a deep impression on me.
9: I love this book! Worth owning and reading again and again.
8. Loved it.
7. Very good.
6. This is good for fans of its genre or author.
5. A not-read-again book. Okay, but not worth it.
1-4: Don't read! I loathed this one.
Basically, the books rated 7-10 are ones I want to own and reread.