The mega-novel is a pinnacle of the storyteller’s craft. When a writer appears who can really create one, it will always be a major event. Gwynne’s six-figure deal is a sign publishers are ready to invest in big stories, but there’s more to reading than bingeing on epics. If the fantasy genre, and fiction more widely, wants to remain healthy, it needs to nurture all kinds of stories. There are great fantasy short stories, novellas and single novels that deserve much wider audiences, but are sidelined by the industry’s unhealthy fixation with the serial format. It’s time for the fantasy genre to tell some new – shorter – stories.
I don't know that I even agree that "the mega-novel is a pinnacle of the storyteller’s craft", for the simple reason that not all longer stories are better ones. Length is not depth or profundity, nor does it even make for more absorbing storytelling. The mere 200 or so pages of Yasushi Inoue's Tun-huang are some of the most spellbinding I've ever read, even if the language is dry by today's pumped-up, overblown standards.
Longer cycles of novels are not a storytelling innovation but a publishing innovation. The industry has such thin margins as it is, they have to do something to keep people coming back, so why not make one novel do the work of five? It's a tactic akin to what ice cream makers used to do, when they pumped air into their product to double its volume, and thus turning one gallon into two. Not that the ice cream tasted any better, of course.
One of the other side effects of this mad quest for ten books where one would do fine is that it does damage to the author. Instead of doing ten different things, and maybe expanding their range or their insights, they're forced to do slight variations on the same thing. Maybe this tactic is justified when there's just so much else to do in this world other than read a book — after all, if you hit on one really intriguing thing, why not milk it for all it's worth? It's always easier to market something that has some degree of existing mindshare than to market something entirely new — although I see that more as a failure of marketing than a failure of the audience.