The Robot City Series
These are books written in Isaac Asimov's Foundation Universe by other authors. They don't progress the overall plot of the Foundation series, they just use some of the concepts and characters to tell similar stories. The books in the series are: 1987: Isaac Asimov's Robot City: Odyssey by Michael P Kube-McDowell 1987: Isaac Asimov's Robot City: Suspicion by Mike McQuay 1987: Isaac Asimov's Robot City: Cyborg by William F. Wu 1988: Isaac Asimov's Robot City: Prodigy by Arthur Byron Cover 1988: Isaac Asimov's Robot City: Refuge by Rob Chilson 1988: Isaac Asimov's Robot City: Perihelion by William F. Wu To be honest these books aren't fantastic and I wouldn't recommend them unless you're trying to get exhaustive coverage of Asimov's Foundation universe.