Continuing Themes And Characters

In Poul Anderson's Psychotechnic History:

"Un-Man" introduces the Rostomily Brotherhood;

"The Snows of Ganymede" introduces the Order of Planetary Engineers;

"Brake" features a Planetary Engineer who is a Rostomily Brother.

"Gypsy" introduces the Nomads;

"The Pirate" introduces Trevelyan Micah of the Coordination Service;

in The Peregrine, Trevelyan joins the Nomads.

Thus, series give stories more substance. 

The only continuing characters in this future history series are:

Etienne Fourre in "Marius" and "Un-Man";

Trevelyan as above;

a colonial family in "The Acolytes" and "The Green Thumb."

This post has referred to nine of the twenty plus instalments in the Psychotechnic History, depending on how we count them.