1 Star -- I finished it. That's about the only good thing I can say about it. It's over.
2 Stars -- Enjoyable in a few places. But had some flaws or quirks that annoyed me. Not hideous. But more frustrating than satisfying.
2.5 Stars -- Enjoyable in more than a few places. Yet something was missing that kept me from really enjoying this one. Almost but not quite.
3 Stars -- A good, solid, nice, enjoyable read. A respectable rating. The norm. Nothing to be ashamed about. A book I'd be happy to recommend to others.
3.5 Stars -- Overall a nice read, but there were a few special places that made it "pop." A character here or there. Or a unique plot twist. A clever phrase. A book that whenever it comes up you think, "Oh, I liked that one. It was fun."
3.75 Stars -- A good book. An enjoyable book. One that I enjoyed reading, and often didn't want to put it down. A book that at the time you're reading it seems really good. But that usually simmers down to just plain "good" in a few weeks or a few months.
4 Stars -- Now we're talking really really good. Beginning to merge into outstandingly good. The book is definitely one I'm wanting to recommend. Pure pleasure to read. Satisfying. Left you happy and wanting more.
4.5 Stars -- A book that was not only good--but was great. A book that leaves you with a lot of adjectives. It might be "Powerful" or "Memorable" or "Authentic" or "Incredible." But it is a book that makes an impact on you. You want to talk about it. You want to write about it. You want to share the joy and spread the love.
4.75 Stars -- A book that is beyond incredible, beyond good. A great book. A wow book.
5 Stars -- The wowiest of the WOW. A book that you can't just believe is that good, that perfect. We're talking books that are practically perfect in every way. Books that you want to reread again and again. OR else books that while you might not reread, the experience was so intense that you're never going to forget it. The characters. The story. It's a part of you. These are books that you keep talking about, keep thinking about long after you've read them.
Special note. 5 Stars that make it the ultimate, ultimate, favorite, favorite, best best best book ever list get this image.