Since this novel is an odd blend of romantic and realistic elements (see the "Genre" section for more information on this), it makes sense the style would be a bit of a smorgasbord as well. There's something here for everyone. Check out this passage, where we can see a lot of different style elements at work:
"O – Tamsie," said the elder, weeping, "I don't like to let you go."
"I – I – am –." Thomasin began, giving way likewise. Bu quelling her grief, she said, "Good-bye!" again and went on.
Then Mrs. Yeobright saw a little figure wending its way between the scratching furze-bushes, and diminishing far up the valley – a pale-blue spot in a vast field of neutral brown, solitary and undefended except by the power of her own hope.
But the worst feature in the case was one which did not appear in the landscape; it was the man. (2.8.44-46)
First off, we have some interesting dialogue. In this dialogue, Hardy uses realism and attention to detail – these characters are speaking like people who are actually upset, rather than delivering long, eloquent speeches about how depressed they are. Throughout the novel, we see attention paid to local slang and accents, people's tendencies to stutter or say things they don't really mean, and so on.
We also get a different kind of detail in the nature descriptions and the strong imagery, which is loaded with symbolic meaning. Thomasin is facing doom here, but rather than just say "Thomasin is sad because she is doomed," Hardy lets imagery get the point across for him. We see Thomasin swallowed up by the "neutral" colored heath, which implies that the heath, and the world itself, is indifferent towards Thomasin's plight. At the end, we also shift to Mrs. Yeobright's perspective more fully and learn about the ominous "man" she sees. The man may not interrupt the landscape and Thomasin's solitude, but his presence is still largely felt in the scene.
This is a very visual novel in a lot of ways – we get very long passages with just the narrator talking and relatively little dialogue. Check out Eustacia's introduction chapter (1.7), where the narrator just describes her in acute detail the entire time. There's also the beginning of the entire novel, where we just get page after page of detail and imagery about the heath.
So how does detail work in this novel? Well, we have a lot of romantic imagery and details – Eustacia is compared to things like queens and goddesses in her introduction. We also have attention paid to two other kinds of detail in the style:
When he had again regained his van he lit the lantern, and with an apathetic face at once began to pull off his best clothes, till in the course of a few minutes he reappeared as the confirmed and irretrievable reddleman that he had seemed before. (2.7.88)
Hardy often gives us very detailed physical descriptions, such as how people look, what they're doing, and the imagery of the heath. And we often have to infer emotional details from the physical descriptions we get. This isn't to say that Hardy doesn't psychoanalyze his cast or provide us with up-front emotional details. But in terms of style, it's worth noting that he often pulls back some and lets us do more of the emotional guess-work on our own.
So, in this passage, we see a very careful use of diction and a subtle use of detail that lets us know what is going on with Diggory Venn. The word "again" lets us know that Diggory is returning (a major theme) to his van, and thus to his old life; and this return is packed with meaning. Instead of moving on to a new and better life, Diggory "at once" begins to change clothes and he quickly transforms back into the reddleman "he had seemed before." The "he had seemed" part is very crucial here, since it implies that Diggory is in a sort of reddleman disguise and that he's really a type of person who's not defined by being a reddleman. Finally, we get a tiny clue as to Diggory's emotional state through the word "apathetic," which means uncaring or numb.
So on a sentence and paragraph level we have different sorts of details all functioning together to give us a rich picture of these characters and where they live. Hardy uses words very carefully and alternates between emotional, physical, romantic, and realistic details in the style. This novel relies a lot on imagery, symbolism, and sometimes subtle hints as to what's going on and who's doing or thinking what.
In a broader sense, we have two other style elements to consider: epic and theatrical. In the passage with Thomasin, quoted above, there was a sense of epic, even cinematic, sweep to the scene. It also concluded a section in the chapter and functioned as a sort of mini-climax and a quick scene-break – we get a short transitional paragraph about Thomasin's marriage and then proceed onwards to a follow-up scene with Clym and Mrs. Yeobright. The chapters in this novel are all styled like individual scenes in a play and tend to revolve around common themes. The volumes, meanwhile, function as full acts in a play. We have other examples of theatrical elements in this novel as well: namely, monologues and soliloquies.
"And I have no money to go alone! And if I could, what comfort to me? I must drag on next year, as I have dragged on this year, and the year after that as before. How I have tried to be a splendid woman, and how destiny has been against me!" (5.7.20)
Eustacia is speaking like she's actually in a play, directing her words towards some unseen audience. We even see this type of style crop up during conversations, in which characters speak outward towards an unseen audience rather than to one another. This is also a comment on how people have a hard time communicating and understanding one another – check out the "Language and Communication" themes for more information.
It's worth noting that the narrator could've just told us what Eustacia was thinking, rather than have her deliver a lengthy monologue, which also functions as the climax to the scene. We pointed out the realistic dialogue between Thomasin and Mrs. Yeobright earlier. But this novel also has lots of stylistic shifts where characters speak more like dramatic actors than real people, and the bi-play between the two speaking styles sort of represents the varied style of the novel overall.
Another major style element that ties into this sense of the theatrical and the dramatic is suspense. We often jump forward in time to different scenes and get little clues about developments and new events before having them confirmed. So how is this suspense accomplished in terms of style? Let's check out this scene, where we follow Clym on a walk.
Minute after minute passed by, perhaps ten minute spased, and the shadow on the moon perceptibly widened. He heard a rustling on his left hand, a cloaked figure with an upturned face appeared at the base of the Barrow, and Clym descended. In a moment the figure was in his arms, and his lips upon hers.
"My Eustacia!" (3.4.5-6)
There's a lot of lead-up to the scene's climactic moment, where it's confirmed that Clym and Eustacia are secretly dating. And we get a lot of clues and details that there's more to this scene than Clym just communing with nature (which, given this novel, may have actually been the truth). The emphasis on time here, for instance, implies that Clym is actively waiting for someone instead of just enjoying the lunar eclipse.
Finally, we have a strong sense of the epic in the novel. A lot of the epic is set up through mythology references, through the setting, and through chapter titles like "The First Act in a Timeworn Drama." It seems like this story has happened before and these characters are playing out designated parts in a saga (for more details on this, check out the "Fate and Free Will" theme section). But we also get very dramatic individual scenes that are styled in an epic way.
On inclining into the latter path Yeobright felt a creeping chilliness, familiar enough to most people, and probably caused by the unsunned morning air. In after days he thought of it as a thing of singular significance. (5.2.71)
This is a definite stylistic break, where the narrator hints at future events and the fact that doom is definitely approaching. In a way, this small sentence helps to offset the coming scenes that lead up to Eustacia's death and it lets us know that we're about to enter some new dramatic territory.
But Hardy likes to disrupt expectations on occasion and he especially tends to undermine his sense of the epic, even as he spends a lot of time setting it up in the first place. He often uses irony and humor to shift the tone and style, and to cut away from the sort of high melodrama of the more epic passages in the novel. The humorous remark Hardy uses often feature direct narrative address (where the author talks directly to the reader) and a different sentence style.
That she would behold face to face the owner of the awakening voice [...] was most unlikely, unless she were to haunt the environs of his mother's house like a robin, to do which was difficult and unseemly. (2.4.1)
Hardy undercuts the epic love story that he set up in the previous chapter, referenced by the "awakening" voice, by basically mocking Eustacia's would-be stalker tendencies. One last style element to point out here: Hardy is a huge fan of metaphors and similes, and he frequently uses comparisons between characters and nature details (like the robin) to get various themes and plot points across to the reader.
Overall the style fluctuates a good bit in this novel – not enough to be jarring, but enough to show a whole lot of complexity and a lot of different styles at work.