Change In Future Histories

Any particular instalment of a future history series may be:

set in a future period but without advancing the historical process;

a transition to a later period and a new sub-series of the history.

Thus, in Robert Heinlein's Future History, several stories set interchangeably in a period of interplanetary travel are followed by a single novel in which the Prophets, having come to power between volumes, are now overthrown. (But one interplanetary story does name the First Prophet before he comes to power.)

Thus also, in Poul Anderson's Technic History, Nicholas van Rijn has six instalments, including one novel, entirely to himself quite apart from his interactions with David Falkayn and other continuing characters. At first glance, the Technic History might look like little more than the van Rijn and Flandry series stuck together. And indeed van Rijn and Flandry do take up a lot of the space. However, keep reading and The Technic Civilization, Volume III, Rise of the Terran Empire, by recounting several intermediate stages, shows how one historical epoch replaces another.