The adventures of Derec and Katherine who we learn is Ariel continue. After saving the city and figuring out the death of David in book 2, they decide the next course of action is to find a way off the planet. They begin by searching for the key to perihelion that got them to Robot City, and later they learn of more humans in the city and shift their focus to looking for them and the ship that brought them.

Three different authors for the books, but the style is the same. I think they are trying to imitate the style of Asimov, especially the style of his robot stories. They mention over and over First Law, Second Law, etc. It results in a kind of stilted dialog when the humans talk to the robots. It's one of the reasons I think these books could be classified in young adult. I don't have a problem with reading YA novels, they can be excellent. I think that Derek and Ariel may miss some arguments they could make. If they really wanted to get off the planet, they could use Ariel's medical condition and her need to see a specialist (not available in Robot City) as a reason for the robots to help her find a way off back to civilization.

Still the book was enjoyable, I like the characters, and the reading goes quickly.