Wells, Heinlein And Anderson

The two high points of sf, I think, are:

futuristic speculation, including future histories;

time travel, which can involve futuristic speculation, historical fiction and paradoxes.

Thus, HG Well's The Time Machine incorporates futuristic speculation and an imaginative description of what amounts to a kind of time dilation and implies temporal paradoxes. Wells' characters discuss visiting ancient Greece and the Battle of Hastings although they do not venture into the past, at least not in the course of this single narrative. There is some speculation as to when the Time Traveller went on the second journey from which he did not return. Of course, Wells also wrote several other works of futuristic speculation, including the future history, The Shape Of Things To Come.

Heinlein as a successor of Wells:

the Future History and other futuristic novels;

three independent narrative statements of the circular causality paradox, all involving the future, not the past.

Anderson as a successor of Heinlein:

eight future histories and many other futuristic works;

time travel - six volumes (if we count the Time Patrol as two) covering prehistorical, historical and future periods and both of the time travel paradoxes;

future history and time travel interacting in the Maurai History and There Will Be Time.

The Time Patrol series, even if (arguably) ultimately incoherent, is not blatantly and obviously so like some other works dealing with "changing the past."

Thus, Wells, Heinlein and Anderson form a three-stage progression. In different ways, Anderson's Time Patrol agents, including Manse Everard, and mutant time travellers, including Jack Havig, are ultimate successors of Wells' Time Traveller.