"Nothing new in the novel has happened since 1922." Or so says critic Anton Bates. He was referring to the publication of James Joyce's Ulysses, a novel which in effect exhausted the possibility of the novel. Do you think Bates was right? Save for Joyce's own Finnegans Wake (which really doesn't qualify as a book except that it's printed on pages and has a cover), I can't think of anything that's "new" in the traditional print medium of the novel.
I agree with Bates that Ulysses marks the end of the novel as a form. The primary reason, I think, is the medium we are using right now, the word processor. Because society is so inundated with information, and writing has been made so technically easy through technology, society is more focused on the expansion of new mediums.
I took a Postcolonial Theory class in which we read "Salam Pax: A Diary of and Ordinary Iraqi". The book was a print version of a blog that had been kept by, supposedly, an Iraqi man throughout the war. The shere volume and availability of quick art and information diminished the motivation to read and right novels at all. It's a true tragedy.
Yes, content really is the sticky point here: postcolonial themes, characters, and settings have pretty much dominated serious literature since 1970 (and even earlier if you consider the boom in Latin American literature to be postcolonial). So in that case, absolutely: the novel is reborn, refreshed, renewed practically every minute with something new--a way of seeing or a way of knowing that is seemingly "other" than our own.
But I have a sneaking suspicion that is not enough. When we talk about "the novel" or "the short story" or "the sonnet," content must inevitably be set aside in favor of form, for it's form that really is the defining characteristic of the genre. The subject matter of Ulysses could have been written as a short story or a poem or a screenplay. What's being told is not very important here: it's the telling that Bates is concerned with. And it's our ability to tell stories in new ways that appears exhausted at this point in the literary history of the novel.
So Quixote, though a hoot, is not much more than an extended episodic novel, one that built upon the tradition of Spanish literature but didn't really contain it. Ulysses, on the other hand, built upon tradition but fixed, practically neutered, it for the rest of us. So sure, you could say that's just different in a matter of degrees...but the degrees are so extreme that the novel itself became different in kind.
I guess it depends on what you consider "new". Certainly, technically speaking, it would be tough to truly innovate in terms of form post-Ulysses.
However, new emotions, stories, ideas, etc. have been produced in the novel form every year since 1922 at an astonishing clip. It's this potential that makes the novel such a great form, it's always new, even if it hasn't been technically updated for a long time. If there was one genre or movement I'd point to specifically, it's the rise of World Literature in the novel form. Writers such as Chinua Achebe and Naguib Mahfouz have, using the same basic form, brought totally new perspectives and ideas to the literate world.
And, if you really think about it, Ulysses carried the novel to its logical conclusion, but how "new" is it, technically, from Don Quixote? Is it a matter of degrees? And, if so, what does "new" even mean in the context of the novel?