The question itself is amazing.
Good prose will, of course, convey ideas; but over and above that, it is music. It is interesting and amusing to know which of Scheherezade's tales
Rimsky-Korsakov's music was "illustrating", but it is beautiful music even if we are ignorant of its provenance. Finely wrought prose pleases us by the art of its construction, to the extent that well-made prose should fall well on the ear even in a language we do not know, owing to the natural fall of cadences, alliteration and assonance, and that sort of thing.
When we combine the music of it with its ability to convey imagery, both sensory and psychological, craftsmanlike prose is sheer pleasure. I--and I daresay I am not alone--will read with great pleasure a work on almost any subject that is rendered in intelligent prose; but a subject must be most exigent before I will submit to reading about it in wooden prose.
I will add what should not need saying, but which often does: finely wrought prose is not "purple" or over-ornamented. Indeed, while some varieites of luxuriant prose can be apealing, usually it is the leans, sparse, muscular sort that pleases best (though Hemingway may have overdone it a wee bit).
Consider these rather different samples just from one writer, Lord Dunsany (the master of fantasy):
"One day the King turned to the women that danced and said to them: 'Dance no more,' and those that bore the wine in jewelled cups he sent away. The palace of King Ebalon was emptied of sound of song and there rose the voices of heralds crying in the streets to find the prophets of the land."
"And now the sun had set, and all the colours of the world and heaven had held a festival with him, and slipped one by one away before the imminent approach of night. The parrots had all flown home to the jungle on either bank, the monkeys in rows in safety on high branches of the trees were silent and asleep, the fireflies in the deeps of the forest were going up and down, and the great stars came gleaming out to look on the face of Yann."
"When the advertiser saw the cathedral spires over the downs in the distance, he looked at them and wept. If only,' he said, 'this were an advertisement of Beefo, so nice, so nutritious, try it in your soup, ladies like it."
(That last is the entire text of Dunsany's story aptly titled "What We Have Come To").
Very, very different but still admirable in different dimensions is this from R. A. Lafferty:
Flip O'Grady was a chimpanzee of mature years and unusual intelligence. He stood a full four feet tall. He was employed as a penny-flipper at the Probability Division: it was under the direction of Doctor Velikov Vonk, and so was Flip. . . .
The flipping was dogged hard work as Flip O'Grady did it, steep psychic stuff with preternatural aspects, and he sweat a lot on the assignments. He wore a T shirt and boxer shorts when he flipped pennies. After every flipping session he took a brisk five-minute shower. Then he put on horn-pipe pants and sports jacket for a forty minute coffee-and-doughnuts break. He took most of his breaks in the International House of Doughnuts, but also in Speedster's Cafe and in Zabotski's Bagelrees. The flipping, the shower, and the break constituted a cycle.
Flip lived in a little cottage that was eight feet by eight feet square. It was really a 'Garden Giant Little Gem Prefabricated Tool Shed,' the deluxe or two-window model. Flip had fixed it up according to his own exceptional taste, painted in three tones, and with red simulated tiles on the roof. It was heaped and overgrown with flowers.
Or, yet again different, this, from a source left as an exercise for the student:
The time was middle morning; rain had darkened the black cobblestone pavement. Six-wheel drays lumbered along the streets; the entire district sounded to a subdued hum of engines. As Gersen walked a short sharp bleat of whistle signalled a change of shift; the sidewalks at once became crowded with workers. They were pale people, blank and humorless of face, wearing warm well-made coveralls in one of three colors: gray, dark blue, or mustard yellow; a contrasting belt, either black or white; black round-topped kaftans. All were standard issue, the government being an elaborate syndicalism, as thoroughgoing, careful, and humorless as its constituency.
The point of intruding those examples is that while style and tone can vary considerably, well-wrought prose specimens have much in common. For a contrast, consider this, from a quite popular SF&F author:
He was on the right track. Coming through the hills I had been considering going after the group left at the southern approach. Not till Swan spoke did I realize that I would be unable to sneak up on that group. Night had come. Night belonged to Shadowspinner. He would know where we were and where we were headed. Unless that was away from him he would be waiting when we arrived.
It reads like a telegram, or an entry in the annual (tongue-in-cheek) Hemingway sound-alike contest.
Saving that last, give me the quoted sample, and I'm on that tale like a hungry dog on a bone, and I don't very much care what it's about. (That second quotation from Dunsany is probably the quintessence of words meant to be spoken aloud; one can just hear, say, Richard Burton doing it.)
I was assuming that "plot" in this discussion means the actual events in the story, and in Gormenghast's case there is very little actually happening over a very long period of time. If you stripped away the prose, the unique characters and setting and the themes of Gormenghast, you really wouldn't have much left. "Titus Alone" is especially uneven in terms of plot (which is not a criticism of the book, I know it wasn't finished. But I doubt many would read it for the plot).
