Can you put your readers right in the middle of things without assuming they know anything? Let's take a very strange world with very unique world building like Made by Abyss or The Elder's Scrolls: Morrowind, can you take your readers right in the middle of things and name things that are known by the denizens of your world, but not your readers as though they knew everything and just expect them to read your book a second, third or even read a companion book, or should you reveal things step by step? Is this shock approach of just putting your readers in the middle of things ever done by a successful author?
One example of a successful book that does this really strongly is Ninefox Gambit by Yoon Ha Lee. Lee drops you straight into an battle scene that very heavily uses in-universe "exotic technologies" which are very magical, different from anything genre-conventional and hard to wrap your head around, but that are normal for the POV characters. Rereading the first chapter, there is a tiny bit of infodump about things like the fact that adherence to a specific timekeeping system makes the technology work, but you're still thrown pretty much into the deep end. (And IIRC the fact that the specific timekeeping system involves ritualized torture is both the fundamental core of that universe and dealt out to you in dribs and drabs.)
(An interesting example of a nonfiction book that does something like this is Birth of a Theorem by mathematician Cédric Villani, which is an autobiographical account of his research leading up to his winning a Fields Medal (most prestigious prize in mathematics, think along the lines of Nobel Prize). The mathematics of it is both a huge part of the book and going to be completely incomprehensible to the vast, vast majority of readers, but I still found it an engaging book with a plotline I could follow.)
Honestly, I think doing this can make your book significantly more of a draw. I've talked about this before, but your #1 goal in the first chapter is to keep your readers hooked. They need to want to know what's on the next page, they need to be invested in some questions they want the book to answer. Those questions can be character-related, they can be plot-related, but they can also be worldbuilding-related. "Wait, what's this insert-fantasy-language-here thing and why is the POV character so desperate to steal it?" can serve as a minor hook. On the flip side, infodumping can actively work against you: by answering questions before the reader is curious about the answer, creating sections which don't advance plot or character and slow momentum, or actively weakening character development because infodumps often break POV.
The trick, of course, is to straddle the line between this and just outright losing the readers. The basic rule of thumb you need here is find a way to communicate exactly what the reader needs to know to understand the scene they're in and to make it compelling without breaking flow. Taking Morrowind for an example: if your character is travelling on foot, you can mention that they're trying to keep under cover and keeping a wary eye towards the sky for cliff racers. That gives the reader enough to know that there's some air-borne threat the character is trying to avoid, which adds suspense to the scene as a whole. You can seed some character detail here (how scared the character is, how they react to that fear, etc.) or setting detail (trying to hide under the caps of the mushroom trees, seeing Red Mountain on the horizon when they check the sky). You do not need to go in detail about what a cliff racer is exactly to do any of that, and doing so would most likely weaken the scene as a whole. On the flip side, if you just write your character walking along and then suddenly, a cliff racer attacks! you're in more of a pickle - the reader has absolutely zero context for the cliff racer built up, has no clue how large one is and what's going to happen and why there's something attacking in the first place, and you're going to have to give enough detail for them to understand that without breaking the flow of the action. A much harder task, especially if the character is familiar with cliff racers and can't echo the reader's suprise/shock/lack of understanding.
One important thing to note here is that readers' tolerances here vary. I've seen reviews of Ninefox Gambit that said the reader couldn't get into the book because they were hit with too much unexplained stuff at the start, but it's a hugely successful book and I loved it to pieces. I'm fairly far on the other side of the spectrum - I read fanfic in fandoms I don't know for fun and have abandoned published novels in the first chapter because it became clear that the author wanted to spoon-feed me every bit of information; the detective work of figuring out bits about the world and character from context is one of my favourite reading experiences and if you deprive me of that you'll probably lose me. So you probably want to keep a target audience in mind and keep the level of deep end vs infodump fairly constant throughout.
Putting your reader right in the middle of the world, without preface or explanation, is a hallmark of mastery of world-building.
This is because it forces the author to inhabit their character's life in order to share their motivations as they interact with the fantastical world.
Read the first chapter of 'The Golden Compass' -- follow the look inside -- and examine how Phillip Pullman shows you Lyra's world. There is not any explanation of what Pantalaimon is beyond being a daemon -- which gets no definition. Major elements of the world are just dropped on the table without explanation -- Dust, Scholars, a severed child -- and the story is engrossing. I think this is because the author only provides just enough information about world elements as they come up. That we learn much about the world from how the characters in the story react to them. Later we get more detailed explanations, but as the story advances we consistent get just enough information to put the new element in sufficient context that we can accept it and keep moving through the story.
Similarly, Anthony Burgess's 'A Clockwork Orange,' throws the reader right into the middle of the story with the main character's first person narration in an argot of English, Russian and French that is almost impenetrable but conveys a lot of emotion and intent.
Another example is the first thirty pages of 'A Diamond Age' by Neal Stephenson that introduces a technological world very different from our own without the least bit of explanation and is totally engaging. His characters use phrases like 'The Feed' and skullgun and cripplers without any explanation, but because the context is understandable and the details aren't important when these elements are introduced, everything works to make a great story.
Most certainly, if you do it right.
David Drake's With the Lightnings drops you right into the lives of two characters with no build up or warning. They are where they are, doing whatever it is that's going on that day.
With the Lightnings is the first of a series that ran to thirteen books. I've read them all. The introduction in the first chapter of With the Lightnings was, to me, very effective. It showed me two very different characters in an interesting setting with interesting backgrounds - and made me want to learn more about them.
Drake has both characters doing something.
Daniel Leary is making his way through a foreign city, with a specific (though not specifically named goal) in mind.
Adele Mundy is attempting to organize a bunch of uncooperative workers in a newly founded library.
While both characters are going about their tasks, random thoughts of the past flit through their minds. The current activity and the thoughts of the past meld together, leaving a dynamic flow instead of a static info dump.
I find the mixture natural and believable. Characters in Drake's stories tend to think of things while carrying out routine tasks, just as normal people do. When the situation gets tense, they focus on now and doing what has to be done, with the occassional flitting thought that they don't really have time for, but that comes anyway.
The characters' thoughts deliver some background, but not all at once. You get little sketches of the people and the background delivered in a constant stream with the action of the curent time providing the flow.
I greatly enjoy Drake's style. I have all of the RCN (Daniel Leary and Adele Mundy) books, and I've read them all many times. I also have most of the books from Drake's Hammer's Slammers series - also very good stories.
You can download a free eBook copy of With the Lightnings directly from the publisher at the link above.
Yes, this is done all the time. Often the trick to this is easier than you might guess: You take some task that is already familiar to readers. A meal, getting up and getting ready for work, eating or drinking something for breakfast, going to work, entertaining themselves, shopping for groceries, whatever.
And add your modern or magical or alien immersion to that.
The familiarity of a general task orients the reader and lets them guess what the magic is doing. Star Trek never explains a "sonic shower", but the purpose is obvious from the familiar context. Or a "Transporter", or "Warp Drive", or "Dilithium Crystal", etc.
When you name things known by the denizens of the world, do that in a context that gives the reader some clue. We are good at inferring a meaning from the context in which a word is used, if not once then in a few contexts in which people use it.