There are stories that are good stories. There are stories that are good stories on their own that are not good shared world stories. There are even stories that are probably worth reading that are good shared world stories that are fairly bad stories standing on their own. The sliders on this kind of fiction can be all over the place.
What Was a Good Story that Was a Bad Shared World Story?
One series immediately comes to mine when thinking of a good story that was a bad shared world story. Its' been years since I read them, but the Prism Pentad series of Dark Sun novels immediately leap to mind.
From a novel reader's point of view, this was a broad sweeping epic. The world referenced all sorts of classic fantasy, but was more akin to post apocalyptic stories than any of those classic fantasy stories that it referenced. It has massive secrets and plot twists. Epic things happened to the characters and the world, and nothing was safe. Anyone could die, anyone could be changed forever.
And almost all of those things are what made the books a terrible start for a shared world franchise. The Dark Sun setting had just been established. We knew the rulers, the cities, the recent history, what was carried over from classic fantasy and what was turned on its head. It was a wide open playground where people could deal with political maneuvering lost lore or ancient magic, and find all kinds of secrets around every corner.
But the book revealed a lot of those secrets. We knew from the setting what history A looked like (vaguely) and what current history C looked like, but we didn't know B (the path between them). The Prism Pentad had a lot of B in it. Which would be fine if the author would have been the only one directing the setting, but he wasn't.
We learned who the Dragon was, who the Sorcerer Kings were, saw the social order overturned in multiple established cities, learned some of how we got from classic fantasy to post apocalyptic fantasy, delved into the nature of magic, and found out who the mysterious big (sort of) bad guys were. All secrets that could have been hinted at for years by other authors without confirming anything.
But strictly as a reader of the series? I loved it.
What Was a Good Shared World Story that Was a Bad Story on its Own?
I had to think about this one a bit. I enjoyed the book, and I don't fault the author with anything in the structure of the book or its resolution, but I would have to say the Star Wars novel Reven fails as a stand alone novel if you weren't already looking for answers or connective tissue in the shared world of the Star Wars Expanded Universe.
Because so much happened in them, the backstory of the characters from Knights of the Old Republic I and II (the video RPGs) is only briefly touched on, so if you don't already have a frame of reference for the characters, you can easily feel like you were missing something. The end of the book isn't really a resolution. We see people end up in certain places after they try to force a resolution, but it really feels like the book should lead into another chapter or a whole other book, but instead, it just ends with an overview of where we leave everyone.
People that are fans of the RPGs knew that the book was going to fill in the gaps from the end of the KOTOR series and the storylines that are explored in the Old Republic MMO, but someone not coming from those games is going to read a story where they are introduced to someone, told, but not really shown, how important and powerful a lot of characters are, and then see them struggle for a while before they end up in limbo at the end.
The book is entertaining, if you know it's not going to tell a full story, but it was clearly created as a bridge between stories being told in another medium, and this could be very jarring if you don't go into the novel with that idea firmly in mind.
Plentiful Potential Pitfalls
I think it's really important to know what you want to do with your shared world when you set out to tell stories there. Are you promoting another product beyond the novels, comics, or storytellying medium where you are publishing your narrative, such as a roleplaying game? Are those coequal endeavors? Is one clearly part of the marketing of another?
I've seen a lot of shared worlds advance their timelines, and I'm not sure why. While I'm sure you can have a shared world where there is a meta-plot that you want to advance, and you are funneling your creators into that meta-plot, that's a very specific kind of shared world experience, and I think one that is outside of the usual experience that people are looking for. It makes sense for Star Wars, for example, because the shared world is based on an ongoing, forward moving narrative itself. It makes less sense for lines that support RPG settings, because while you may be pushing consumers to buy new, forward moving projects, you are also making some of your old products less attractive, and potentially changing elements in the setting that actually attracted fans.
Media Properties that Move Forward
Continuing my recent trend of imagining myself in charge of important things I'll never get near, if I were going to be in charge of a media property that is planning to move forward, I think I would be much more careful about the pacing of that property.
There have been several properties, from the Forgotten Realms to Star Wars, that told stories where authors are writing installments of an ongoing narrative even as other authors are finishing earlier parts of the narrative. Often characters don't feel the same between books, plot threads get dropped, and the story feels uneven.
If at all possible, I'd make sure that I really knew that I needed to maintain that pace before I forced that many authors to read each other's minds. In a 9 book arc for example, why not have the same author do a trilogy, and plan for a specific thematic shift between them, thus minimizing the potential pitfalls of shifting the voice of the characters at a crucial point.
Properties that Sell a Setting
Again, if I'm in charge? Resist the urge to move forward. If your property is the setting, and not a group of heroes or a specific narrative, don't move past the era that you started in unless you have to do so, and then don't race ahead too fast.
Try to tell stories that are a day in the life of the people in the setting. If you feature adventurers, don't have them save the world, have them save Important Guy #14, or stop a plot that could get worse. While this would be important advice for a property based on an RPG setting, it's still relevant to a more traditional shared world, because if one author's character saves the world, the next author might be very tempted to at least keep up the same pace and have his characters save the world, and eventually you have a world in constant peril, which suddenly feels commonplace instead of noteworthy.
If you are promoting an RPG line, the above advice is even more important. Your adventurers should never seem like THE heroes of the setting, just SOME heroes of the setting. If you have a D&D style setting, they should be competent, mid level types that get the job done, not high level movers and shakers. They can have interesting adventures, but not at the expense of revealing secrets or toppling the big bads that you should be saving for other people that will be using you setting.