But, for me at least, the drive to enjoy a shared world fictional universe isn't just in having one brilliant novel that is the Best Thing Ever Written in this Genre. I mean, if an author can pull that off, it's great. But it's not entirely what I'm looking for. In fact, there are times that an author that does their job too well as an author of an original story might screw things up as an author of shared world fiction.
Shared world fiction, to me, is about building a universe that is consistent, that I know, and that I recognize when different authors use that universe. Shared world authors have a lot to juggle to do their jobs right, because its not just about having a decent plot, good characters, and exciting pacing. Its about mentioning a city that already exists in the setting, and having what has been true about that city in the past be true in this book as well. Its about a reference to an organization bringing with it the connotation of what that organization's reputation is as it has been portrayed in other books.
Not only does the shared world author need to juggle the usual demands of being a good author with the demands of making consistent references to the setting and building a few references of their own, they also have to make sure that they can quickly summarize enough information for new readers without creating an info dump for established fans. You don't want your setting so obtuse that only people that have been with you right from the start can follow along, but you don't want to reinvent the wheel with every story either.
Single authors can end their series, kill off important characters with impunity, and break all of their own toys. They may or may not actually do this, but they do have the freedom to do so. Shared world authors have to work hard to make their current characters important, their own events compelling, so that if they break their own toys, you care about them, but you aren't yanked out of the narrative because some element shows up that you know isn't "theirs" and therefore is likely safe.
A good shared world book isn't just good because the author is good, it's good because whomever the caretaker of that shared world is has set the right boundaries and let the right things show up, and kept the wrong things off the table as the story develops. It might be very compelling to have a dragon destroy the City of All Important Crossroads, but what is it going to do for the shared world? Its not that it shouldn't be done, but is one good story worth throwing out a consistent touchstone that many authors have consistently used?
Is the world big enough to tell the kinds of stories you want to be told? If you have people in one story saving the world, and then the next story is about characters saving the world, again, next week, have you just lessened the impact of the last story? Do you have to have another story about saving the world? Couldn't it just be about saving a person, a town, a city, a country? If the story is big enough, are you prepared to have the ramifications of that story be mentioned in the rest of the shared world fiction? After all, if the City of All Important Crossroads was destroyed but the world was saved, and then another group of adventurers save the world again next week, but never mention the dragon attack or the world saving, what is the point of having both stories in the same universe? Is it really a shared world if you have your individual author's storylines so compartmentalized that they cannot impact one another.
When a shared world setting can juggle all of the above, and do it reasonably well, for someone that really wants that kind of experience, it is a very special kind of escapism. You don't just picture the world as the author reveals it, but when the main character walks past a given alley, you know what's there. When someone mentions they were born in a given region, you know what kind of accent they might have. When someone mentions that a trade caravan ins't going to reach the city from a faraway land, you know what kind of food won't be served for the next few weeks.
It's not easy. It's not for everyone. But when it works, it creates an attachment to the setting that is deep. Writing a story in that setting isn't just about telling the story, but about cultivating the world itself and handing it off in a condition that allows another author to take the world and run with it.