This is definitely one of the greatest, most intriguing and enjoyable light novels I have ever read. I started with watching the anime to get some kind of idea of the feel of the story. The anime itself was pretty good and made me read the light novel. Now compared to the light novel the anime is a 7/10, because the light novel is a definite 10.

FOR ANIME WATCHERS: I recommend reading from the first novel if you have already seen the anime. First you will probably notice that Ayanokouji's personality is a little different than in the anime, more normal-like. This is for most of the first three novels, but even during the first three novels you see small slips and clues of his real personality, which you anime watchers will probably appreciate. His True personality comes to light by the end of the third novel. This development literally BLEW MY MIND. It made me appreciate Ayanakouji as a character a whole lot more than in the anime and made him seem even more badass. Also a bonus, in the light novel you'll get to see some other character development from the real best girl of class D (SPOILER: Her initials_K.K. and it isn't Kushieda or Horikita).

Now on to my personal review of the light novel:

Art 8/10: okey I will start with art because that's easiest. So, the art is pretty good, it illustrates the characters well and gives you a good idea of the situation. It isn't what this light novel is popular for, but is still good.

Story 10/10: The story is about a student Ayanokouji Kiyotaka who just entered an unusual high school. It is later revealed that for the next three years of high school life they will be in an all out class war to graduate as the best class, class A. The classes are ranked from A-D, and Ayanoukouji is a student from class D, the lowest class. The school determines the rankings for Classes based on school points, which also form the basis of their allowance. School points that each class receives are determined by merit, such as exam scores, behavior, sport clubs,..
Ayanokouji hides his true abilities to not stand out and lead a peaceful high school life, but soon is forced to help the class in secret. He becomes something like the puppet master of Class D while he makes sure someone else in the class gets all the credit for his achievements so he doesn't stand out. This light novel isn't some kind of isekai action packed story. It is a story of mystery, action (in some ways), and suspense. The story of each light novel is great and keeps me longing to read the next one. That's why it is most definitely a 10.

Characters 10/10: This is a completely story-and character driven series with its main character Ayanoukoji Kiyotaka. He is my favourite light novel charater ever. His personality is mainly cold and manipulative, but strangely understandable in the later novels. He also shows rare moments of compassion to certain characters.
(NOTE: Light SPOILERS rest of paragraph)
The two most noteworthy characters other than Ayanokouji are in my opinion Ryuuen and Karuizawa Kei (AKA Best Girl). Ryuuen is the Tyrant of Class C who rules the class with an iron fist and uses backhanded, lowly methods to advance in the class rankings. He is quite interesting as a character and fun to read about. Then you have Karuizawa Kei, the leader of the girls in Class D. She doesn't do anything noteworthy for the first three novels but really starts to shine as a character after volume 4. After volume 4 she and Ayanokouji become close and develop the most interesting relationship Ayanokouji has compared to the other classmates. But I won't go too far into that because that will spoil the story a little.
Other than that you have Horikita (who I personally dislike) the somewhat "leader" of Class D who Ayanokouji helps to benefit Class D in the class wars.

Enjoyment 10/10: As I said, this is one of my all time favorite light novels with great characters and a gripping story. I couldn't resist but write a review of how great these light novels were/are to me. I highly recommend this novel for almost all light novel readers.