There is a state called "absorption" or "flow" in Western culture that athletes and psychologists always talk about. The phrasing can be like, "when you're absorbed in an activity you lose self-awareness, or awareness of the activity being distinct from the self," and so on. You can "forget" you're playing a game, in this sense.
You can say that absorption is about attention. Players have a conscious mind that pulls them around. It focuses on different things. Sometimes only a small portion is "turned on" at any point. Absorbing a player, making them "forget" about life, is about giving something for every piece of their consciousness to care about. If you can make them very alert, increasing their conscious capacity, and give them a lot of stuff to focus on, that's even better. You can watch a movie and forget you're watching a movie, then meet a girl and really
forget about the rest of your life.
Good stories form relationships between the readers' lives and the events of the story, by talking about universal truths, then explaining them in a way that makes them easy to understand. If the story-world is internally consistent, if it follows some logic that doesn't disobey the rules the player has come to expect, then the reader won't break from it. If it talks about relevant things, the reader will be motivated to care in the first place.
There's some function between a players own experiences and the ideas in a story, through which players find relationships i.e. "relate," and feel stuff when they read. Keep a simple function, and don't break it, and your world will be consistent. Talk about universals and it will be relatable.
Example: If your buddy is sarcastic and indicates his sarcasm through context, which you recognize from your experiences, then you will understand and appreciate his sarcasm when he uses it. If you don't understand this function - situation IN, sarcasm yes/no OUT - then you might misinterpret his meaning and lose its value. If he changes the function unexpectedly, like being sarcastic at an usual time, you'll "break" immersion in him, and it won't be great, unless of course surprising shit is a comfortable thing with you.
Games "break" immersion when they do shit that doesn't make sense.
Universals are things that are at the center of experiences. Feel something strongly, understand the core cause of the feeling, then recreate it for the player by reproducing the cause in a new context.
Everyone wants to rage a little. God of War gets to the center of that idea and makes the whole game about feeling like you're destroying shit, then bigger shit, and, "aahhhhh. RRRRRAAAAA. ... die." To make a game more interesting than God of War you need a feeling more relatable than blind rage, then express it clearly, like God of War did (hint: this is possible).
Kids relate to Harry Potter because he's a kid trapped in a boring life who's under-appreciated, then gets whisked away where the dullness of reality is replaced by imagination, where he is very important, and regularly engages in things that the regular people, "muggles," just wouldn't understand, further accentuating his "untapped" secret incredible-ness. What kid can't relate to that? Also, J.K. Rowling writes briskly, clearly, understands what the most important parts are, and makes it very easy to follow along without redundancies.
I'm trying to narrow it down to one important thing, but all I've been able to conclude is that it relies on flesh and blood events...
thing? You ready?
Imagine the whole world feeling better than they have ever felt ever, beyond what a normal human has ever thought possible even at the height of their existence. Humanity is still diverse. What are the central ideas at the center of everyone's lives? What are the thoughts that power our state of heaven-on-earth? What are the common elements between those thoughts?
Okay? Figured it out?
Now express those ideas in simple terms, and optimize the rate at which you transfer those ideas to your player's minds. Oh, and make sure everyone can understand it all equally.
Ideas are big things. Universal Truths are endless. So you'd have to be in constant state of transmitting-ideas-to-the-player forever, always explaining the right slice of your idea at the right time to the right person so... that they relate - meaning they understand - in an optimized time-frame.
(Absorption is about relating Truth)