Sure, there is an Overlord manga. It expands on the story and characters from the original light novel series, giving fans another way to enjoy the world of Overlord.
Overlord is actually both. The light novel provided the foundation and the manga was created based on it. While they share the core concepts and characters, there can be differences in the presentation and emphasis in each medium.
The manga is better in terms of immediate visual impact. The art is really good and it can quickly draw you into the story. You can see the epic battles and the cool character designs right away. But the novel has its own charm. It offers a more complete and immersive experience in the long run. It's like building a relationship with the story and the characters over time. So, if you're someone who values the overall story and character development deeply, the novel is the way to go. But if you're more about the here - now and the visuals, the manga is a great option.