πI recommend you a novel called Demon City, which is also a sci-fi-interstellar civilization novel. The background of the story was a long-term war between humans and robots. The robots had a fortress called " Demon City ", and the humans 'main goal was to destroy this fortress. The protagonist was a young soldier. After he was injured in battle, he was transformed into a cyborg and entered the Demon City for a secret mission. In the process, he discovered a bigger conspiracy and secret information between humans and robots. He had to take a huge risk to uncover the truth and save humanity. I hope you like my recommendation.π