Poul Anderson presents mutant immortals in
The Boat Of A Million Years and mutant time travellers in
There Will Be Time. Far from bring successive instalments of a single series, these works are the exact opposite of that: alternative speculations. An immortal can remember a historical period but not revisit it whereas a time traveller who does not remember a period can visit it for the first time. Thus, history plays different roles in these narratives, as also in the same author's historical novels.
Fictional characters sometimes experience time travel very differently. Anderson's Time Patrollers, seated on timecycles, experience what is to them an instantaneous transition from one set of spatiotemporal coordinates to another whereas the protagonists in Anderson's "Flight to Forever" are enclosed within their vehicle, called a "time projector," while external events fast forward around them. Anderson's mutant time travellers, travelling by will power alone, see the rest of the world fast forwarding or rewinding around them as does HG Wells' Time Traveller and this is not surprising because we are to understand that it was one of the mutants who gave the time travel idea to Wells.
Some completed bodies of work are straightforward boxed set material like four volumes of The King Of Ys, four of Harvest Of Stars, three of The Last Viking etc whereas others are not what readers would expect like:
three Maurai future history short stories;
one long Maurai novel;
There Will Be Time in which the Maurai History is fiction -
- or:
two Kith future history short stories;
a long novel presenting an alternative Kith history -
- or:
A Midsummer Tempest in which Holger Danske from Three Hearts And Three Lions and Valeria Matuchek from Operation Otherworld meet in the inter-universal inn, the Old Phoenix, from "House Rule " and "Losers' Night."
Reading through any of these sequences gets you to somewhere completely unpredictable.