Heh. See, this is why I asked the question originally. Clearly there is a wide range of what readers/writers accept and do with regard to backgrounds and authenticity. I personally will chuck a book across the room because the worldbuilding is unbearably stupid. I don't care how good the characters are. Worldbuilding is such a huge part of story, or should be, that it bugs me a lot when it's unsupportable in any reality.
What you know informs what you write, but certainly isn't the only thing you can write about. My point is, you don't have to go create a whole new language like Tolkien, but if you're making up words and names you should have a good idea of how languages work. He was a language expert and did it for fun, and it is undeniable that his expertise lends LOTR a layer of something extra. Most really memorable fantasies have at least one thing that stands out for them that is usually founded in the author's expertise at *something*. That one thing that makes it different is often what gets it published.
Peter, you said, "The popular, quasi-European medieval background which sits behind so many fantasy works is, in historical terms, little more than pastiche." That is, unfortunately, true, and contributes to a complaint I actually hear a lot at conventions and from industry insiders--that everything on the shelves is beginning to look alike. Perhaps my tastes have been jaded over the years because a) I have read a LOT of fantasy and b) I've workshopped for years, working with many beginning writers who clearly have swallowed all the stereotypes whole and never, EVER do a lick of research. I find myself buying less fantasy because it does look alike, and the beginners keep lifting big elements out of it--and doing it worse. There is often nothing plausible about their worlds, which, unfortunately, as you've noted, often applies to published work as well. The story does not always carry these books well enough to make me swallow the poor worldbuilding. And you can and do lose whole chunks of an audience that way. A friend of mine recounted her reaction (and that of most of her friends) to a historical novel set in her home state of Hawaii, wherein the author named her Hawaiin princess something that had an "R" in it. There is no R in the Hawaiin language. I guess it just sounded good to her. That book never made it out of the store, let alone into the hands of people who might have enjoyed and recommended the story. Research does count.
Peter said, "...presumably either a) your books focus on what you already know very well or b) it must take you a very long time to write each book due to the sheer volume of research you will have to do to make every detail right. And even then, you won't be anything close to an expert in all of these different areas - you'll still be dropping enormous clangers left, right and centre."
Eh, no. I have a degree in history and a broad background in a lot of areas from life experience that I call on, and what I don't know I research. I cut down the time involved by choosing situations and world settings that complement what I know and digging in where I need to. I can paddle a canoe but not sail a boat. If I had to transport my characters by water they would go as passengers or in some conveyance I feel confident writing about. I would construct my plot in a manner that doesn't thrust them into having to sail the thing; or, if it was unavoidable, I would make them as inept as I would be...or, I would go and take sailing lessons to learn enough to make their managing the thing plausible. The point is to understand what you're writing, not just stick stuff in and hope it's good enough to pass muster. Clearly a lot of readers don't care. A lot of us do.
About the armored knights with Kalashnikovs? Since I write alternate history sometimes, bring it on! But it would have to have a thoroughly plausible reason for how the knights got the guns.
For me, yeah, fantasy is fantasy, and you can make up a lot of interesting stuff--so long as it has a logical, coherent underlying structure. And that usually comes from understanding how the pieces fit together--like how your medieval kingdom came to have paved roads, "bales" of hay, and flush toilets. Tripping over that kind of stuff (yeah, I've seen all of those in manuscripts for critique) makes me giggle but also makes me sad for the sheer ignorance of the writer who assumes that stuff just appears from nowhere with no technological foundation for it.
If you look up some of the many, and hysterically funny, lists of fantasy stereotypes, you'll find I'm not the only one who is kinda tired of the cliches and skimpy worldbuilding in fantasy.
Okay, I'm done. It's been fun batting this back and forth!
