Below is the rating structure that I created based on my own personal opinion. It ranges from one to five stars (one being the lowest and five being the highest). My ratings are not bias at all. It only depends on whether the book is good and up to my standards or not.
Rated 5: Magnificent book, would recommend it and has no faults
Rated 4: Amazing book, has very little faults
Rated 3: Mediocre book, wouldn't read it again
Rated 2: Unimpressed, wouldn't recommend it at all!
Rated 1: Overflowing with faults, would never open it again or recommend it!