Don’t see how in the world you can film this for $5M.
Maybe be like Ed Wood and use a lot of stock footage (trains etc.)? :)
A lot of it is them talking in offices and hotel rooms. This is very cheap to film. It will also be the big problem with a film made from the story. Much of the story is dialogue. If they’re going to turn it into something that keeps the audience interested over a long time, they’re going to have to take a lot of liberties.