I am looking for a good account for the development of modern fantasy, something like this section on Wikipedia, just bigger and covering newer authors like GRRM or Glen Cook (you know an article is outdated when you have to call those two new). A book would also be fine (if it's in print).
In case people don't understand what I am asking: I want to know why the books we read today are the way they are? For example, why are there stock race like elves, dwarves in some books? Was this solely because of LoTR or maybe the success of D&D board games contributed to this? When did fantasy begin publishing "dark" works (like ASoIaF)? Was GRRM's success a pathbreaker that allowed writers like Bakker and Abercrombie? Did the boom in sci-fi TV shows and movies in the 70s influence fantasy writing in any way? Is Ursula LeGuin's nearly as influential as it is made out to be?
I am pretty sure somebody would have written articles/books on this subject. I am looking for people to forward me to some such article/book.