1 & 2 star - I don't use these ratings, I just stop reading a book if I don't like it, and I wouldn't rate a book that I'd read only a small part of

3 stars - good book but probably wouldn't reread and would only recommend it if it perfectly fit the request

4 stars - very good book that I can see myself rereading and would readily recommend

5 stars - great book, will recommend, will purchase if I don't already own it

I rate purely on enjoyment, my enjoyment is mostly based on how good the writing is, how it affects my mental state (including negatively), and how much of a page-turner it is.