This was a book I looked decades for in either English or German and never came across a copy until I recently searched again, but this time for digital copies and easily found a one for under 2$ on Kindle! I had read the script and seen the movie many times and finally was able to compare the film to the source material.
Von Harbou wrote the book with a film adaptation (by her then husband, Fritz lang) in mind and it was serialized in a magazine as way to get the story out to the public as pre-publicity for the upcoming film.
The story and characters are pretty much the same overall, thought Joh Frederson, the Master of Metropolis, is more fleshed out and has a mother who makes it very clear that he has become a terrible person after the death of his wife after the birth of their son, Freder who he adores but shows little emotion to.
Another difference is the religious symbolism, heavily Christian - but sprinkled with other mythologies throughout. It is something not really seen in the film and a little overdone. As it was written in 1925 there are also some lines of racism and quite a bit of sexism thrown in for good measure, thankfully missing from the film. The biggest was a huge surprise for me, the absence of the film's iconic message: "There can be no understanding between the hand and the brains unless the heart acts as mediator."
The robot, so iconic in the film is less here and is much more human-like in the novel, It arrives on the scene already made, can talk and begs Joh Fredersen to give her a face. She still gets the face of the Maria the defect leader of the poor and the love interest but her role is smaller and a little muddled in book form.
Well worth a read if you never have and having read the script long before any restorations of the film were done, this would have been an amazing revelation as to the many missing elements from the presentations of the movie I was seeing at small theatres and church basements in the early 80s.