That's exactly right! The graphic novel lacked a proper three-act structure and was more atmospheric. I combined some characters, and added in many plot points and new scenes. With the graphic novel, I knew the basic beginning, and basic end of the story, but I needed to fill out the dramatic action with a lot of scenes I extrapolated from what the graphic novel hinted at, to motivate the story towards the general arcs of the book. I also changed the ending, to make it less pessimistic (slightly). There can be a lot of rebuilding in these kinds of adaptations... it's easier for a new writer to take on the task, I think, lest the original author be too close to the material and not be able to spark new ideas that riff on or tear out the original work.