It could be about the cults and the unholy practices associated with Dagon in Lovecraft's stories. The graphic novel may show the slow descent into madness of the protagonists as they uncover the secrets related to Dagon. It might also depict the grotesque and alien landscapes that are characteristic of Lovecraft's writing.
You can try looking for it in specialized comic book stores. They usually have a good selection of graphic novels, including ones based on Lovecraft's works.