Uh, the people who WROTE the books are likely to be involved in this project. Why the hell wouldn't they be, unless they're from outside Bungie.
Because Hollywood is pompous and clique-ish.... it's resistant to new blood because that usually puts someone else out of a job. So you start to get producers, directors, and screenwriters, all with their own solid network that they don't want to disrupt.
Ultimately, this creates the Hollywood Ego.... the belief among the disseparate individuals that work in the industry that they - the studios and all those connected with them - are the penultimate creative force in the universe. If they ever get their hands on any new material, they have to do it "their way", because any other way is inferior.
Think about it.... if you acquire the rights to a video game, what costumes do you have to design? None... they're there, in the game. Characters? Shit, the game has the characters. Set design? Just play the game. Storyboards? Use screenshots from the game engine, for fuck's sake!
But that's not good enough for Hollywood, no.... all THAT came from "outside", so they have to add "their own personal touch".... which usually drifts so far from the material that you wonder why they licensed the material to begin with.