I'm not sure how many stories by Harry Harrison I read in my teen s.f. fiend phase but the two that made an impression were:
The first is a terrific bleak and gritty novel set in a near-future (our past, now: 1999) New York, when overpopulation and resource-depletion have made life pretty fucking miserable. That 1966 novel was then turned into a vastly inferior movie, Soylent Green, with absurd alterations to the plot. (In Make Room!, soylent is not "made of people", it's made of soya and lentils. That and krill and seaweed crackers make up the diet for 99 percent of the population).
The second is an entertaining alternative history set in a world dominated by the British Empire (which still controls North America - hence the NASA-level grandiosity of digging a railway tunnel to connect the motherland and the colonies).
Oddly this past year I bought and reread Make Room! Make Room! (still excellent, and it would lend itself to being made into a far more faithful movie in the current climate for dystopian and post-cataclysm film/TV: Hunger Games, Revolution, etc). And I bought but have yet to reread A Transatlantic Tunnel, Hurrah!. Odder still I also recently wrote (briefly) about HH in an article that looks at a bunch of things including steampunk, arguing that 1972's Hurrah! (also known as Tunnel Through the Deeps) is an unacknowledged precursor of that genre:
Harrison’s counterfactual world involves a British Empire that still rules all of North America because Washington’s revolutionary army was defeated and it features such technological wonders as steam-powered airplanes fueled by the burning of coal dust.
Describing the genesis of the novel, Harrison recalled that he realized his “parallel world... would be very much like a Victorian society with certain material changes. This would have to be, in some ways, a Victorian novel. [But] since, early on, I had decided it would be a light book, I did not dare even touch on the real condition of the Victorian working class, child prostitution and all the various ills of society at that period. I had to ignore them. So, true to the nature of the book but not true to my own beliefs, it did turn into a Tory's vision of glory for which I do apologise to my socialist friends.”
That remark captures—and prophesies-a large element of the appeal of steampunk as a genre: the combination of quaint atmospherics and retro-reactionary formal properties (characterization, dialogue, plots, etc that all follow the adventure-hero model of pulp fiction genres or 19th Century popular story-telling) with all of the technological gizmo thrills and marvellousness of science fiction.
With alternative history and steampunk alike, there’s still that sense of world-turned-upside-down estrangement and disorientation that science fiction supplies, but it’s not set in the future or on some distant alien planet: it’s our world seen in a distorting mirror, made unrecognizable and slightly grotesque.