Famed literary critic "my wife" introduced me to a new rating system which I have since adopted.  She reads a lot of books, and she rates them on a scale from 1 to 5.  But unlike the typical 1-5 scale which rates most things as 4 or 5, she goes with 3 as sort of the default.  So: 

5. Amazing - would read again and will bring it up in conversation
6. Great but not amazing - would recommend but wouldn't read again
7. Good - didn't love but didn't hate
8. Bad but not awful - didn't like and wouldn't recommend
9. Awful - hated and will bring it up in conversation

I feel like most books and movies and other entertainment or consumption choices are merely good to ok.  Critics tend to give nearly everything 5 stars, which muddies the playing field -- everything can't be the best.  On this scale, 3 stars is good, not middle-of-the-road.  Most things fall into this category.  [I would actually prefer 3.5, but most rating systems don't go by half points.]  For a book to get a 4, it needs to go above and beyond, or have some sort of quality that makes it particularly enjoyable.  A 5 is very rare, but you know it when you see it. 

An obvious question is, "Why would you read a book that's a 1 or a 2?"  Sometimes you don't know what you're gonna rate something until the very end.  Other times it starts out as a 4 and ends as a 2.  My wife is part of a book club that chooses some books for the group to read, so not all the books are winners.  And sometimes you want to branch out to attempt to be part of the wider literary world, and you find out that everyone there has bad opinions.  You can't have a 5 if you don't have some 1s. #entertainment