Foundation Novels reading order (in order of publication date)

10. Foundation (1951).

11. Foundation and Empire (1952).

12. Second Foundation (1953).

13. Foundation's Edge (1982).

14. Foundation and Earth (1983).

9. Prelude to Foundation (1988).

[9a. Forward the Foundation (1993).]
[9b. Foundation's Fear (1997).] The first novel in the Second Foundation Trilogy, it was written by Gregory Benford. Takes place after the first chapter of Forward the Foundation.
[9c. Foundation and Chaos (1998).] The second novel in the Second Foundation Trilogy, written by Greg Bear. Takes place at the approximate time of Hari Seldon's trial.
[9d. Foundation's Triumph (previously titled Third Foundation and Secret Foundation) (1999).] The third novel in the Second Foundation Trilogy, written by David Brin.