Poetic
Melville loved him some Shakespeare, and he often writes like he's in a toe-to-toe poetry-a-thon with the Bard. You could just about declaim many of his sentences to the upper galleries:
Battered and mouldy, the castellated forecastle seemed some ancient turret, long ago taken by assault, and then left to decay. (3.11)
Or listen to the alliterative "s" sounds here:
Sometimes, to be sure, I could not, for the very soul of me, avoid falling into sudden spasmodic passions with him. (2.86)
Even dialogue is often rendered in a heightened, repetitive, formal prose:
Yes…those slits in Atufal's ears once held wedges of gold; but poor Babo here, in his own land, was only a poor slave; a black man's slave was Babo, who now is the white's. (3.107)
For those used to more prosy prose styles, this can all get a bit high-falutin'. Just say, "Sometimes, Bartleby really annoyed me," why don't you, Melville, and be done with it! But the poetic prose really is part of the pleasure in Melville; it's fun to watch the sentences rise and fall like titantic waves upon a teeming shore. Try reading some of it aloud, like you would with Shakespeare. Melville would thank you (elaborately.)