It's been a while since I've discussed any genre-related opinion, so today lets look at the sub-genre of alt-history.
Alternate history is where the author takes one defining moment in history and changes the outcome to explore the ramifications. For instance, what if the South had won the Civil War? What if Hitler had been able to repel the Allies at Normandy during WWII? What if the colonies had lost the Revolutionary War--for my readers from the U.K. this is aka the American Rebellion.
I am currently exploring my first alt-history story idea. It's not an easy sub-genre to write. It not only requires an understanding of what really happened and why, it also requires careful thought about what the effects of changing on outcome might be.
Alt-history is a funny sub-genre because it doesn't have a neat fit into Novy's speculative fiction spectrum (a concept I should fully develop and publish). Briefly, my spectrum has High Fantasy on the left, Hard SF on the right, with non-genre contemporary popular fiction taking the center position. Much of Speculative Fiction falls very neatly on this spectrum, with another group straddling the center.
Although certainly speculative and well-entrenched as a sub-genre, it doesn't fit well anywhere on my spectrum. Depending on how history becomes different, a story could have a finger on the spectrum. Eric Flint's 1632 uses unexplained alien technology to transport a county-sized chunk of the modern U.S. to 1632 Europe. After the change, however, his events fall naturally from the interaction of the history and the characters. Only the first 50 pages or so fall on the spectrum. The rest fits nowhere.
Other writers like Harry Turtledove change an outcome and just let events roll. There is no question of the speculative nature of the sub-genre. It asks the required question: what if?
Perhaps the spectrum needs a second axis to hold all of todays speculative fiction. Perhaps. Or perhaps the subgenre makes good use of being just a couple of points (the mathematical definition) left (fantastic side) or right (scientific side) of the center.