DelRey published this very thick Essential Superman Encyclopedia in 2010. The book is full of characters, places and items from the vast Superman mythology.
Among the long forgotten places of Superman lore that have an entry in this book are Quasmania (from Superman #11 in 1943), Kronis (from Superman Family #187 in 1978 and Quetzatlan (from Action Comics #103 from 1946).
The encyclopedia was written by Robert Greenberger and Martin Pasko. Pictured are both the paperback and hardcover versions.