Exiles at the Well of Souls (1978) is the first book in the Well World series by late Science Fiction author Jack Chalker. Supercriminal Mavra Chang goes after a ruthless syndicate boss who has seized a god-like supercomputer. Unexpectedly she and others find themselves on the Well World where magic and science hold sway. They undergo transformations into different creatures as they try to escape.

Tremendous world building. The Well World consists of different hexes with different rules - in some magic works, in some science dominates. A vast range of creatures in different habitats. A friend of mine used the names of the hexes as his passwords.

So solid escapist fun as the protagonists encounter vivid creatures and settings.