Okay, so the DF is basically my favourite series and it seriously motivates me to write, but there are still some things I don't understand (yet) about the fantasy market.

There are stories you write and show other people because they're fun to read, but when does that translate into something that an editor would say: Yep, this is something we'd publish? I'm not sure if I just haven't escaped the horrors of the literary/academic crowd at university but I'm still struggling to understand where "interesting ideas to you and your friends and folks online" meets "publishable".

Is interesting normal people from beginning to end all the idea has to do? Or is there some other element that I'm missing, minus writing mechancis?

I understand everything related to writing mechanics (that stuff's generally quantifiable) but I'm still not clear on when what a story is about becomes recognisably book-worthy. Note that I do understand that it has to somehow appeal to enough people to be worth taking a financial risk, but I'm really wondering about the kinds of stories themselves.

What if you wanted to write a saga about demon warlords? An S&S story about a prince who travels across a magical continent (on a giant crow with a house strapped to its back)? A boy who accidentally kills a girl in his class, resurrects her as a zombie and somehow has to figure out a permanent soluton before she starts to rot?

There are ideas that are intriguing to, say, your average gamer or anyone who likes imaginativeness, but I have no idea when a story has reached a point where most sane editors will say, "Yeah, this works." I haven't seen any articles or editors who go into this in detail -- all I've found is vague stuff like "has to be compelling" and "I gotta love it", but that tells me absolutely nothing useable whatsoever, lol.

I still don't know what kinds of stories and subject matters I'm free to work on if I want to stand a chance at being published.