Stephen Baxter
The keeper of British SF's cosmological flame: the bridge from Wells, Stapledon and Clarke to the modern field, and the standard for fiction in which the universe's full history is the stage.
Alternate History
What-if worlds where history took the other fork: Axis victories, surviving Romes and timelines gone sideways.
The authors (5)
Philip K. Dick
The genre's great metaphysician.
Michael Moorcock
Twice a revolutionary: as editor he made the New Wave happen, and as writer he rewired heroic fantasy with Elric, whose shadow falls on every brooding anti-hero with a cursed weapon since.
Kim Stanley Robinson
The standard-bearer for utopian hard SF and the writer who made climate fiction a serious policy conversation.
Neal Stephenson
The bridge between cyberpunk and Silicon Valley's self-image: the Metaverse, Google Earth's acknowledged inspiration (Snow Crash's Earth software) and a tech-industry readership that treats his novels as product roadmaps.
Essential books, oldest first (4)
The Man in the High Castle
Hugo winner (1963), the novel that legitimised alternate history as serious SF, and the basis of Amazon's long-running 2015 series.
Voyage
Sidewise Award winner for alternate history; NASA-procedural SF's high-water mark, dramatised by the BBC and visibly ancestral to For All Mankind.
Cryptonomicon
Locus winner and a Hugo finalist; the hacker generation's foundational epic, credited with seeding real cypherpunk and cryptocurrency thinking, and gateway to his Baroque Cycle prequels.
The Years of Rice and Salt
Locus winner and a Hugo finalist: the most ambitious counterfactual the genre has produced, and the standard rebuttal to Eurocentric future histories.