My feeling is that I would prefer to write things that have something new to say, and most but not all of the time I would prefer to read things that have something new to say, and there's a place for comfortably familiar and reassuring and a place for new things to say and I'm damned if I'm going to generalise any of that into a prescription for anyone else, beyond a wistful hope that at some point the marketing of SF and fantasy would get better at indicating how much of a given book is which.

I'm not at all minded to work with the kind of fantasy that has elves and dwarves and unicorns and a Dark Lord, because doing it in the manner of the most common take on it has no interest for me. Taking some of those elements and doing something entirely different and worthwhile with them - as frex the Secret Country books do with unicorns - is not without appeal, though. Particularly this stuff about very complicated magic systems. I think there are worthwhile things to be done with trying to capture the feeling of the edge of understanding that one gets being on a particular scientific cutting edge, frex, with a character working on the cutting edge of a complex magic system. I'm not aware of anyone doing anything like that - Lyndon Hardy's Master of the Five Magics is sort of in a similar direction but it feels more like engineering to me.