Moby-Dick is a 600+ page book about the sea, where very little happens and you won't care. It earns its status as a classic not by presenting a nuanced, epic plot or by devoting itself to absolute verisimilitude in its portrayal of the world, but by sheer bravado and a ubiquity matched only by the character/god of the title itself: Moby-Dick reaches out to all regions of the intellect and occupies them in a way that few have come close to doing since.
This isn't to say that Moby-Dick's plot is bad by any means: just minimal. Yet it's hard to imagine another book that, first of all, picks such good minimal elements, and, secondly, makes so much of the minimal elements it picks. Moby-Dick is narrated by Ishmael (a fact announced in one of literature's most famous first lines), a man of sketchy personal history who signs up for a whaling voyage for several reasons, most of which are delineated for us in the book's hyperspeculative first chapter. What he hopes for is some harsh relaxation, an ability to forget the madness of his land-locked America. What he finds is Captain Ahab.
The Impossible Pursuit: Moby Dick
Many literary protagonists--at least the memorable ones--desire the impossible. Caligula wants to hold the moon in his hands, and the result of his frustration in this drives the lunatic energy of Camus's play. Don Quixote wants the world to be something entirely other than what it is, and his incessant insistence on his personal truth makes Don Quixote, by turns, hilarious and pathetic. But rarely is a literary protagonist quite as aggressive in his pursuit of the impossible as Captain Ahab.
Ahab's leg was taken by the White Whale, Moby-Dick, a beast said to be everywhere and everything at once, which naturally makes it quite difficult to exact any meaningful revenge. But Ahab doesn't want to just confront the impossibility that is Moby-Dick; he wants to harpoon it, to take a brilliant light, and turn it--via the hellish capitalistic engine that is his ship, The Pequod--into cheap candles.
What it seems like when Ahab's quest is introduced is a tricky problem for a dedicated hunter; what it seems like--after Melville has done some more work on setting up the theological and semiotic rules of his oceans, most particularly in the chapter "The Whiteness of the Whale"--is nothing less than an effort to demask and murder God. And this is a story that it is extremely difficult to screw up in the telling.
Ahab is assisted in his quest by crewmen at all levels of society: his three mates, their three 1850s-era ethnic harpooner/assistants, a crew spanning all nations, a shadowy assistant who strongly evokes the Devil, a mad chef's assistant, and, skulking somewhere about the rigging, Ishmael, largely absent in plot terms after he signs his life over to Ahab's diabolical quest. Ishmael emerges as the book's narrator: a fanatically erudite and speculative observer of the doings about the Pequod, and the man responsible for forcing order onto chaos.
Ishmael's fairly freewheeling speculations enliven the book. At one point he asserts that a whale can only be a fish; at another he waxes poetic on the similarity between falling into the exposed brain of a dead cetacean and picking up the works of Plato for the first time; in a third he exults in the common brotherhood available to anyone willing to squeeze hunks of spermaceti oil with his fellow men. Of course, his fairly large leaps of logic and common sense tend to derail the plot for several hundred pages at a time.
This would be a huge problem--and is, for some readers (those readers who could probably just read the last twenty pages and be at least semi-satisfied)--were it not for the fact that Ishmael represents Melville at his most rhetorically brilliant, philosophically searching, and comically on-target.