Nowhere is the line between representing the real world and inventing new ones more grey than when writing alternate history. On the one hand you have to craft a setting that is new and coherent, that presents enough novelty to interest readers. On the other hand you have to get a lot of real details right or those knowledgeable about the period will criticise.

Kim Stanley Robinson’s The Years of Rice and Salt shows one response to this challenge, deviating from reality far enough back that the fictional world swiftly becomes very different from what we’re familiar with. Differences from reality don’t undermine plausibility. This approach also suggests that history could have been very different based on a single change.
Harry Turtledove’s Great War series takes a different approach, using so many historical details that you can’t help but be convinced, if occasionally overwhelmed. This is alternate history that suggests a certain level of inevitability, that other historical outcomes would have been similar to our own.
For ‘Odin’s Mirror’ in From a Foreign Shore I took yet another approach. This is a story about someone who doesn’t understand what is happening around him, and so the reader doesn’t need to know the details. I avoided key points like ‘how did this happen?’ because they weren’t what the story was about, and because hopefully readers will be focussed on the character’s perspective and not mind that I’ve fudged the issue. Only time and reviews will tell.
What other ways can you approach world building for alternate history? And what alternate histories have you found convincing or unconvincing? Share your thoughts below.