Okay, what if we had decided to draw the S the other direction back in BC? Would it really make any difference?
Alternative history assumes that history has places where the choices of the few or the many will create a world notably different from ours. Sometimes when you start at one of the pivot points, you get lost following it forward, simply because so many known points in history become lost to us. It’s not easy to set up, though no more difficult to write than any self-constructed world.
Alternative history has, in common with historical fantasy or science fiction, the hurdle that people who know the history you’re messing with will judge you for your story, your speculation, but also for your historicity. Depending on how many centuries forward you run this change, you can get far enough from the known historical cultures that you can get away with a lot of changes. But some critters, standing in for editors and readers, will doubt that some of your changes are in line with the originating culture, that sort of thing.
Most vulnerable are under-researched war changes. Without the Alien Space Bats stepping in, the Nazis are not going to successfully invade Britain, even if they wipe out the RAF, because they still face the Royal Navy and don’t have an invasion fleet like the Allies built for D-Day. AskHistorians and BadHistory have been over this a zillion times. Ditto the Confederacy conquering the Union in the ACW, the first modern industrial war. Napoleon clinging to his throne … well, someone just has to talk him out of that Russian adventure. You have to find the right points to alter.
Is this of interest to readers? Can you get help with the finer points of history, so you don’t have to invoke the Alien Space Bats? The subreddits on Reddit proliferate, starting with Historical What If.
That being said, Alien Space Bats may be exactly what you’re here to write about! This is supposed to be alternative history with speculation in it, whether science fiction or fantasy, not straight counter-factuals. Bring on the time-travellers, the zombie army, the vampire Queen Victoria (with her second husband, Prince Vlad), the artificially-produced helium, the dragon corps, and whatever else you want to have fun with.
These are examples of alternate history:
Seventh Son by Orson Scott Card, the first in a series about Alvin the Maker. The others are:
Red Prophet
Prentice Alvin
Alvin Journeyman
Heartfire
1632 by Eric Flint, which takes the reader, and a whole West Virginia town, back to the Thirty Years War.
The Lord Darcy series by Randall Garrett, which gives us an England still ruled by the Plantagenets where magic is commonplace:
Lord Darcy
Lord Darcy Investigates
Murder and Magic
Too Many Magicians
The Guns of the South by Harry Turtledove, in which racist time travelers offer advanced weaponry to Robert E. Lee so the Confederacy can win the American Civil War.
The Worldwar series by Harry Turtledove, with aliens invading the midst of World War II, forcing the Allies to work with the Axis to save the world.
The following are “straight” alternate histories and so not really what we support, but interesting reads:
Bring the Jubilee by Ward Moore
An acclaimed “what if” the South had won the Civil War by winning at Gettysburg, re-imagining the entire fate of the American continent.
Redcoats’ Revenge: An Alternate History of the War of 1812 by David G. Fitz-Enz
Most people really don’t know how close infant America came to ending up back in the British Empire in 1814. Suppose England had unleashed the Duke of Wellington on the hapless American army?
A Traveller in Time by Alison Uttley
This gentle YA story about an English girl who spends her summer wandering backward to Elizabethan times at the very old manor house where she lives is poignant and haunting. She comes to know some of the people involved in the plot to try to free the imprisoned Mary Queen of Scots, and so forever will regard them as something more than names on the pages of her history books.