Positing infinity, the rest is easy.
The Prince Who Was A Thousand is ... a teleportationist, among other things ... the only one of his kind. He can transport himself, in no time at all, to any place that he can visualize. And he has a very vivid imagination.
Granting that any place you can think of exists somewhere in infinity, if the Prince can think of it too, he is able to visit it. Now, a few theorists claim that the Prince’s visualizing a place and willing himself into it is actually an act of creation. No one knew about the place before, and if the Prince can find it, then perhaps what he really did was make it happen. However, positing infinity, the rest is easy.This contains already the central idea that is expressed more fully in Nine Princes in Amber and subsequent books in that series.
While traveling (shifting) between Shadows, [the prince] can alter reality or create a new reality by choosing which elements of which Shadows to keep or add, and which to subtract.Creatures of Light and Darkness also has obvious similarities to Lord of Light, which many regard as Zelazny's best book and even one of the greatest science fiction novels ever written. Both have been among my favorites since I read them as a kid.
... Sid and some others created a fannish publishing house, Advent Publishers, in 1956. He was a teenager when he helped publish Advent’s first book, Damon Knight’s In Search of Wonder. ...
[Sid] loved SF whereas Einstein deplored it. Lest SF distort pure science and give people the false illusion of scientific understanding, Einstein recommended complete abstinence from any type of science fiction. “I never think of the future. It comes soon enough,” he said.While I've never written science fiction, occasionally my research comes close -- it has at times addressed questions of the form:
Wikipedia: Hard science fiction is a category of science fiction characterized by concern for scientific accuracy and logic.
NYTimes: ... we slowly discover (and those wishing to avoid spoilers should now skip to the start of the next paragraph), the cause of Josie’s mysterious illness is a gene-editing surgery to enhance her intellectual faculties. The procedure carries high risks as well as potential high rewards — the main one being membership in a professional superelite. Those who forgo or simply can’t afford it are essentially consigning themselves to economic serfdom.
WSJ: ... Automation has created a kind of technological apartheid state, which is reinforced by a dangerous “genetic editing” procedure that separates “lifted,” intellectually enhanced children from the abandoned masses of the “unlifted.” Josie is lifted, but the procedure is the cause of her illness, which is often terminal. Her oldest friend and love interest, Rick, is unlifted and so has few prospects despite his obvious brilliance. Her absentee father is an engineer who was outsourced by machines and has since joined a Community, one of the closed groups formed by those lacking social rank. In a conversational aside it is suggested that the Communities have self-sorted along racial lines and are heavily armed.