*: I finished the book, which means I will be rating and reviewing it. But finishing it might be the only attraction of the 1*. It could as easily have got none.
**: I finished it and there must be a paragraph or two, a section or an aspect of the story that I found innovative or attractive.
***: More often than not, 3* denote two kinds of books: those that are not very good but gave me a lot of pleasure (generally due to plot or execution) or those where I know the book is good, but I did not enjoy it. Sometimes, it also denotes books with one major fault (usually length or depth).
****: A very good book, but not a priority for re-reading.
*****: If the eternal recurrence of the same was true, I would not mind reading these over and over again. In the 5*, plot, character, innovation, execution and reading experience come together seamlessly, and one is not privileged over the other.