I want to make it clear right now:
These ratings are only my opinion.
(I'd think this would be obvious, but recent debates about authors reviewing other authors have made me reconsider.)
These ratings (and, more accurately, the long-winded review that precedes them) are a reflection on my reading of the book -- what I do or don't find effective, whether something resonated particularly strongly with me, etc. If you disagree, that's cool! Leave me a comment explaining your perspective on it, and I'd be happy to have a dialogue with you. But the star system itself is mostly for use as a filing system. If it causes undue trouble, I'll just stop using them. Simple as that.
The ratings are far from an exact science, and ultimately I tend to go with my gut, but here's a couple lines on the reasoning behind each one: