My Internet’s been running really slowly this week, and my reigning thesis for why is that most of the bandwidth for my local cable provider is being gobbled up by the ten trillion people all trying to download Diablo III. I don’t blame them: they’ve been waiting over a decade for this thing to come out.

Still, it isn’t just the legacy of any game like this which draws and keeps an audience. It’s “immersivity”, that thing where you steep yourself in something not just once but time and again. I may have my qualms about the value of immersivity over other things, but I can’t deny its massive importance. Especially if you’re creating something you want other people to share.

What is it about a world that makes it immersive? The easy answer is details. But wait: before I get into that, isn’t it redundant to say “an immersive world”? Isn’t all world-building immersive, ipso facto?

I suspect confirmation bias is at work here. We believe world-building to be inherently immersive if only because we remember the immersive world-building best and let the rest of it slide out of mind.

I was recently reading reviews for another entry in the recent glut of young-adult dystopian romances that seem to have become all the rage lately (not to say they’re bad, just that there’s so many of them right now). The more critical reviews hammered on the book for having thin worldbuilding—in other words, there were some gestures in that direction, with some things being banned and so forth, but not much beyond that. There were some details that provided some immersivity, but not on the order of a David Belasco. Not enough there there.

A digression. The automatic shorthand for a dystopia these days seems to be “a world where things we take for granted are banned”, which is cringe-inducing for two reasons. One, it’s a narrow view of what dystopia is about: many dystopias are at least as much about what is not only permitted but mandatory, and not all that is mandatory in dystopia is uncomfortable. (The best way to keep people in a prison is to make it not only comfortable but appealing.) Two, the implications of such a simplified view of dystopian fiction are somewhat insulting: do authors (or editors and publishers) feel younger readers aren’t able to follow or comprehend the politics of a “real” dystopian novel any more? Then again, maybe with these stories it’s just a question of being just immersive enough, because the real value of the work isn’t in its dystopian ambitions but in how well it can use a veneer of such things to give spice to a romance between young lovers.

The opposite of this is the kind of kitchen-sink immersivity that one most often finds in fantasy novel cycles like George R. R. Martin’s Westeros books, or Robert Jordan’s Wheel of Time saga. Everything from a morning meal to the hem of a dress is given lavish screen time on the page, and it’s hard to argue with this approach when it seems to be at least partly responsible for the success of those books. One of the things fans of Martin and Jordan cite most is how all that detail makes you feel like you could step into the worlds they describe, etc. For people who are looking for escape of one kind or another, an ocean of pleasantly alien detail comes as a welcome balm.

But is the most total detail the best kind of detail? I don’t think so. I’d argue that it’s specific, well-chosen detail that matters as much as, if not more so, than a constant wall-to-wall carpeting of elements. We appreciate the full body of details that have added up to create the Star Trek or Star Wars universes, if only because there are so many of them added up over such a long period of time and from so many pieces of work. That said, take any one of those pieces of work—especially the founding pieces: the original Trek series, the 1977 Star Wars—and look at them close-up. They’re redolent with details, but always specific and well-chosen ones that move their respective stories forward. We don’t need to know everything about how warp drive or lightsabers work; we just need to know that they do, and any details about how can wait until the story absolutely demands them.

What makes a story truly immersive isn’t just that the details are there, but that they make you want to know more. People go back to a favorite movie or book to look for all the things they missed the first time. Sometimes those things are as much projections of the reader as they are the work of the creator, but the presence of that magnetism is unmistakable.