Not long after finishing The Blue Wolf I looked at the other books waiting on my shelf for their turn. Most of them are books in translation as well — e.g., The Scarlet Gang of Asakusa, about which I find myself constantly writing an opening paragraph to discuss the book and then throwing it out five minutes later.
Most of them are also fairly short. Of all the books on that shelf, I don't think two of them are more than three hundred pages — and one that is, is a graphic novel (Solanin). I don't see this as a drawback, either from the point of view of a reader or a writer. If a good book is short, I'm inclined to believe that's because the author knew exactly what story to tell.
The Blue Wolf (and Tun-Huang before it) told broadly-expansive stories in only a couple of hundred pages. They are worlds removed, both in storytelling style and length, from the massive bricks that most people associate with historical fiction. In fact, there's another historical epic about Chinggis Khan (Genghis), which runs to three five-hundred-plus page volumes. I haven't yet read it, but if it follows the pattern I've come to associate with these sorts of books, its strategy will be to assume that length equals immersion — that the way to draw a reader into a story is to write a really long story, and give them little choice but to maximize their investment of time.
The problem is, it often backfires. Length can inspire just as much skimming and indifference as it does close reading and absorption. The nadir of this sort of thing is The Wheel of Time, where we're told a giant and hopelessly involved story mostly for the sake of telling us a giant and hopelessly involved story. Another motive, I fear, is compulsively putting one over Tolkien, the para-Freudian motive for most "fantasy" authors today: kill Dad and take his place on the bestseller list and in the fan wikis.
I'm not trying to construct an argument against longer stories, but rather against using length as an automatic given: that an Epic Story has to be of a corresponding Epic Length. I have to wonder how much of that is the influence of marketing: if you have a pitch for a historical novel about the life of Chinggis Khan, why just get one book out of it when you can get three? Never mind the potential damage done to the narrative by compulsively inflating it, like pumping up a car's tire until it bursts.