There are many things Dostoevsky is good at. But you know what is pretty much universally acknowledged? Dude is no kind of prose stylist. On the one hand you've got your Chekhovs, your Dickenses, your Balzacs. And on the other? You've got this guy, whose every sentence feels like it's taking a hammer to your skull while yelling "get it? get it? get it?" It's, um, it's not the most beautiful we've ever seen.
Some key features that put the Do in Dostoevsky tend to be used to make readers be really on edge and thus totally receptive to all the psycho yelling the man is laying down. To make this happen, one technique is to transition what sounds like normal dialogue into some kind of surreal space where we don't know what on earth anyone is going to say next. Check out how this conversation between the Ivolgins goes from bad to worse as they talk about Ganya's possible marriage to Nastasya, right before she herself invades their house and non-hilarity really ensues:
Ganya stood and frowned, he expected a family scene. He never thought of apologizing to the prince, however.
"If it's all settled, Ganya, then of course Mr. Ptitsyn is right," said Mrs. Ivolgin. "Don't frown. You need not worry yourself, Ganya; I shall ask you no questions. […] but you can hardly expect your sister—"
"My sister again," cried Ganya, looking at her with contempt and almost hate. "Look here, mother, I have already given you my word that I shall always respect you fully and absolutely, and so shall everyone else in this house, be it who it may, who shall cross this threshold."
Ganya was so much relieved that he gazed at his mother almost affectionately. […]
"Now I will only ask you one question. […] How could you so blind her?" Mrs. Ivolgin's question betrayed intense annoyance.
Ganya waited a moment and then said, without taking the trouble to conceal the irony of his tone: "There you are, mother, you are always like that. You begin by promising that there are to be no reproaches or insinuations or questions, and here you are beginning them at once […]"
Ganya's irritation increased with every word he uttered, as he walked up and down the room. […] Ganya's voice was full of the most uncontrolled and uncontrollable irritation.
The prince turned at the door to say something, but perceiving in Ganya's expression that there was but that one drop wanting to make the cup overflow, he changed his mind and left the room […] and opened the door. He started back in amazement—for there stood Nastasya Philipovna. (1.8.125-145)
You can follow the adjectives that describe each speak to see how much the writing reinforces each person's mood. Mrs. Ivolgin goes from resigned ("I shall ask no questions") to annoyed. Ganya goes from frowning to contemptuous to affectionate to pointedly sarcastic to irritated to so irritated he is about to explode. And just in time too—he has reached his point of no return just when Nastasya shows up to really crank up the heat.
Another technique is to start conversation as though we are suddenly catching the characters in the middle of a scene, or in the middle of a conversation where they know what they are talking about and we do not, and to have the dialog itself explain what the characters are doing instead of the narrator. It is disorienting and unusual—and again, great for keeping readers on their toes. Here is an example of what we're talking about from Myshkin's trip to Rogozhin's house:
"All this is mere jealousy—it is some malady of yours, Parfyon! You exaggerate everything," said the prince, excessively agitated. "What are you doing?"
"Let go of it!" said Parfyon, seizing from the prince's hand a knife which the latter had at that moment taken up from the table, where it lay beside the history. […]
"I seem so absent-minded nowadays! Well, good-bye—I can't remember what I wanted to say—good-bye!"
"Not that way," said Rogozhin.
"There, I've forgotten that too!"
"This way—come along—I'll show you." (2.4.122-137)
Every action that happens in this scene is shown first through the dialogue. We have no idea what is happening when Myshkin suddenly yells out "what are you doing?" and Rogozhin answers "let go of it!" The exchange is tense and unpleasantly unexpected. What could be happening? Instead of having the narrator describe Myshkin picking up the knife, we first get the strange sensation of listening to characters speak about something only they can see.
The same thing happens when Myshkin is leaving. It's clear that he has forgotten which way the exit is and Rogozhin decides to show him out, but again—all of this is conveyed with dialogue, and not even particularly expressive dialogue, but instead the very realistic words of people who can see what they are doing, even though we cannot.
The final technique we'll point out is the way Dostoevsky ratchets up the crazy with long, pounding, run-on sentences that make a reader feel almost out of breath just trying to keep up with the syntax. For a good example, check out this pileup of words that signals that Ganya is about to lose it good:
Proud and vainglorious to the point of insecurity, of hypochondria; seeking all those two months for at least some point on which he could rest with a certain dignity and show himself nobly; feeling himself still a novice on the chosen path, who might fail to keep to it; finally, in despair, having resolved to become totally insolent in his own house, where he was a despot, but not daring to show the same resolve before Nastasya Philipovna, who went on confusing him until the last moment and mercilessly kept the upper hand; "an impatient pauper," in Nastasya Philipovna's own phrase, of which he had been informed; having sworn with all possible oaths to exact painful recompense for it later, and at the same time occasionally dreaming childishly to himself of making all ends meet and reconciling all opposites—he now had to drink this terrible cup as well and, above all, at such a moment! (1.9.36)
Look at the way all those commas and semi-colons keep being stacked one on top of the other—the rhythm feels like the shallow and fast breathing of a person who is just about to hit the boiling point.
Also helping the feeling along? The many different and jumbled modifiers. We've got gerunds (everything that ends in "ing" basically), temporal signifiers ("two months," "still," "the last moment," "later," "at the same time"), adjectives and adverbs, a quotation from Nastasya that puts the events into a temporal tailspin (since we get a quick backstory about Ganya being told what she had said, which makes us suddenly shift gears and imagine a time way back when versus now), and even super heavily referential metaphors (Ganya as a despot at a time when the Russia was ruled by actual despots, namely tsars, and Ganya drinking a "terrible cup," which is an echo of what Jesus says when he goes to his execution).
It's tonal madness. And yes, we know that we just used a massive run-on sentence to describe how Dostoevsky uses run-on sentences. Pretty meta, no? And it works—after reading this, our hearts are pounding and our palms are sweaty, and we are ready for some explosive verbal abuse action.