I have read the Light Novel and its subsequent film adaptations and spin-offs. Needless to say, I'm fairly knowledgable in all things Overlord. Now, to get certain things straight:

1. This is NOT an Isekai. Well, it is under that genre, but not like others. The main character, Momonga, is not looking to escape this virtual world, but conquer that. Elaboration on that later.
2. This is NOT for the fainthearted reader. Momonga does not act to exalt evil, but nor is he the perfect protagonist. He does what he needs to do, and if a few insignificant casualties are needed to reach his goal, then so be it. He does not exalt the idea of justice and does not save others to live up to being a hero.

This is what sets Overlord apart. Its main character enters this New World with his guild base, The Great Tomb of Nazarick, filled with powerful beings with undying loyalty to him and the Supreme Beings. To live up to his vassals' expectations, he puts on the persona that an undead Lich King like him should have: powerful and austere. This is what tears him apart inside since he is but a blue-collar salaryman who was thrown into this New World from Yggdrasil.

The author, Maruyama Kugane, said it himself: "The main character of this book is a skeletal magician who leads a vast evil organization, and he is meant to feel like the final boss of a game. Because of that, those readers who don’t believe in saving people without a reward (as is common in LNs or anime) and put themselves first will enjoy this book." By putting this mindset on, we can clearly validate Ainz's actions. He is no longer a human, but an undead skeleton; his appearance overrides his own human notions of right and wrong. The only thing he wants is the betterment of Nazarick. If he has to be good, if he has to be evil, it solely relies on how it will better Nazarick.

Now that I got the storyline and plot out of the way, onto the art. There are no words to describe it. Simply calling it amazing is even a disservice to how well So-bin has created the cover art.

All in all, the Overlord Light Novel trumps all other adaptations with its descriptive dialogue and details which you will never find in the anime and manga. The fact that this light novel exists is a reminder that literature is not dead. There are still writers who will make literary works that beggar the imagination.