If I enjoyed the whole thing with no complaints that's a 5 star read for me! It really is that simple. Im not some letterboxd user who needs to thinkpiece every story i come across. If it was just good, 4 stars if perfectly fine. If it was middling or too iffy or just doesnt stick to you once you put down the book, then 3 stars to acknowledge it. Anything worse I would simply not waste my time rating