The two last, like a number of others, are set in what could loosely be called a standard setting for epic fantasy or sword & sorcery. Hopefully not in a clichéd way — I try to portray a range of different types of pre-gunpowder civilisations, rather than the usual bland blend of something that vaguely passes for a cross between mediaeval Europe and ancient Babylon — but the stories have broadswords, horses, temples to numerous gods and so on.
The Treason of Memory, on the other hand, is set in a culture of flintlocks and rapiers, somewhat reminiscent of Europe in the late 17th/early 18th centuries, while The Lone and Level Sands has more in common with the mid 20th century. This is a long way from broadswords, or even flintlocks, although perhaps not exactly like the equivalent period in the real world: land vehicles are mainly electric, for instance, and air travel comes courtesy of airships.
The Lone and Level Sands is archaeological fantasy. Like parts of the Indiana Jones series, it's set in a desert country in an unstable world where anything could happen. It has elements of a thriller — sinister rivals, trigger-happy soldiers, blackmail and betrayal — as well as the fantasy elements of a temple out of mythology and... well, you'll have to read the story, when it comes out.
Coincidentally, I have another story coming out later this year, in the excellent magazine Aoife's Kiss, which is related to this, to the extent that it's also a view of the same myth from a "modern" world. This time, though, the culture is the computer age of the same world. If you pay attention, you'll find a couple of more specific links between the two.
So what's the advantage of doing it this way? Wouldn't it be simpler to create a world for each story, or at least each series? A pre-gunpowder world, a world of flintlocks, and so on? Just invent what I need, when I need it?
Well, it would be easier in some ways, but I think nowhere near as effective. In a joined-up world, the ideas don't come in isolation, and they don't develop in isolation, either. The legend behind The Lone and Level Sands is (hopefully) effective because it's a story I already knew, and the "modern" discovery has a history that make it comparable to finding a relic from Atlantis in our world.
The background to these stories isn't just a background — it's people and places whose stories I know and have written about. That's a level of reality that's difficult to achieve in a one-story world. Not impossible, but difficult.
The world I use offers me the means to write almost any kind of story I want, from epic fantasy to occult thriller — I've even found a corner to write something resembling steampunk — and stories come into being from the influence of their own past and future. There are stories coming to me that need to belong to a different world, whether it's a one-off or an ongoing world, but I don't anticipate running out of fascination and inspiration in my flexible world anytime soon. Probably never.