> Does one really get anything meaningful out of saying this was a 6-star book vs a 7-star book?

I rate for myself, and not others. And for over 20 years I've used a 10 point system.

10 = Easily amongst my favorite

9 = Awesome, but not in all time favorites

8 = Really liked it, and would recommend

7 = Liked it, was worth my time, but not so much that I would happily recommend to others

6 = Liked it, but wasn't worth my time

5 = Neutral

And below 5 I don't distinguish. I randomly pick to indicate I didn't like it.