I'd like to nominate Metropolis
by Thea von Harbou, the novelization of Fritz Lang's classic film by his wife/collaborator. From a review at Amazon :
Thea von Harbou's book is the indispensable companion to Fritz Lang's immortal film. As most people know, Lang's film was butchered by German and American editors-we have lost about 25% of the film. Essential scenes and many of the subplots were deleted to make it fit within a small time frame. Reality Check: The shorter the film, the more times they can show it, and the more money they collect. Consequently, with the best of restorations, we are seeing a film with as many gaps as a hockey player's smile.
This book, which was serially published before the film's release, fills in the gaps. You get a better sense of the story that Lang and von Harbou are trying the tell. The book allows you to get inside the heads of Freder and co. in a way that the film does not allow. You get a stronger feel for the dystopic milieu that Freder fixes.
This story is essentially mythic, so devotees of Joseph Campbell, George Lucas, and James N. Frey will devour the book and the film. You see the messianic and redemptive elements that makes this story so enduring. This story is one of my favorites, and rates with anything C. S. Lewis, J. R. R. Tolkein wrote, although not with the same level of craftsmanship.
In the public domain. A Feedbooks