I don't think I've actually ever rated anything below 3 stars because I'm good at picking books for myself or gave up on any that would be but here's mine:

1-Awful, mostly likely didn't finish but still feel the need to warn others. Truly nothing redeeming. Potentially hateful content etc.

2- Disliked the book, I don't recommend it but wasn't truly awful

3- An ok book that I wouldn't rush to recommend to anyone but still enjoyed it to some extent

4 - A great book that a loved but has a few flaws/points I didn't like. Didnt wow me from start to finish.

5 - Near perfect, almost life changing. Hard to find any negatives.

And then I have a further tier - favourites shelf which are books that changed my life/ I really want to highlight/ mean something to me.