Well, first, there's the difficulty of translating the written descriptions in the novel into a visual and playable format. For example, if the novel describes a very complex alien species, creating a believable and functional representation in the game can be tough. Also, pacing can be an issue. Novels can have a slow - burn build - up, but games need to engage players quickly. And then there's the matter of dealing with fan expectations. If the game strays too far from the novel, it can face a lot of criticism.