THE COMMODORE By Patrick OBrian Norton. 282 pp. $22.50 IN THE seafaring world of Patrick O'Brian, it's easy to feel like the rankest landlubber, incapable of distinguishing a taffrail from a topgallant, utterly unsure about the exact nature and crucial importance of the weather-gage. There are some pages in Master and Commander -- the first novel in this now 17-part series about a ship's captain and a naval surgeon/intelligence operative during the Napoleonic Wars -- that make William Gass's The Tunnel seem like, well, smooth sailing on a cloudless afternoon.

Reportedly many of the fans of O'Brian's novels about Capt. Jack Aubrey and Dr. Stephen Maturin surround themselves with glossaries, maps, charts and the early 19th-century equivalent of the Blue Jacket's Manual, discovering an old salt's pleasure in working out the details of tall-ship maneuvers and the intricacies of sail-cloth. Others appreciate these volumes as rattling good adventure stories a la Captain Blood. A few critics, however, have gone so far as to call O'Brian the greatest historical novelist of all time.

That may be going too far, but it's hard not to sympathize with the impulse: Despite the nautical jargon, O'Brian's novels are more than sea stories; in fact, this vast roman fleuve, or perhaps one should say roman ocean, stands up to comparison with that most capacious of all 20th-century works of fiction, Proust's In Search of Lost Time. I'm not kidding. In an obvious way, they are of comparable length, focused on a single generation, laced together with flashbacks, echoes and recurrent minor characters. But they also share an apparently boundless fascination with such themes as love and friendship, jealousy, the vagaries of social position, financial and sexual scandal, secret lives, the comedy of personal relations. The very denseness of O'Brian's language -- whether describing a ship's operation or reproducing the talk of Regency bucks and ladies -- recalls Proust's own elaborate descriptions of cathedrals, paintings and dinner parties chez Madame Verdurin (who, I'm sure, must have served as an inspiration for Jack's wonderfully venal and socially ambitious mother-in-law, Mrs. Williams).

Of course, many of these elements may be found in Proust's own model, Balzac, whose rough-and-tumble Comedie Humaine is set only a little later than the Aubrey-Maturin novels. But what clinches the Proustian association is Stephen's love for the free-spirited Diana Villiers, so strongly reminiscent of Swann's passion for the elusive Odette, albeit with a happier outcome. At the very end of Post Captain, when Stephen realizes that his beloved has become the mistress of a noted Jewish financier, he happens to glimpse her at the opera. She is as beautiful as ever, but now she consciously strikes poses. "The purity of wild grace was gone, and the thought that from now on he must associate vulgarity with his idea of her was so painful that for a while he could not think clearly . . ." Gradually, he arrives at the bitter Proustian insight: "The woman in the box over there was not one to whom he would have paid any attention, at any time." Think of Swann when he finally grasps that he has wasted years on a woman "who was not his type."

Does this comparison with In Search of Lost Time seem extravagant? Perhaps a little. Obviously O'Brian doesn't address several of Proust's obsessions -- in particular, the vision of childhood and the vocation of art -- nor does he exhibit a dreamy and relentless psychologizing; but, in compensation, he proffers a lot more in the way of visceral thrills. Consider the opening sentence of Post Captain:

"At first dawn the swathes of rain drifting eastwards across the Channel parted long enough to show that the chase had altered course. The Charwell had been in her wake most of the night, running seven knots in spite of her foul bottom, and now they were not much above a mile and a half apart . . . "

No one with an ounce of romance in his soul could willingly stop reading at this point.

Nevertheless, I admit -- heretical though it be -- to preferring the social comedy and political machinations on land to the undeniable excitement of victories at sea, even though my heart never fails to leap at the battle cry "Beat to quarters." O'Brian's Jane Austen-like humor is especially addictive, being understated, airy and oblique. At the beginning of The Commodore an admiralty official turns to Stephen at dinner and says, "May I help you to one of these kippered herrings, sir? They are uncommon fat and unctuous." Note, as well, the penultimate and perfect word in this otherwise traditional observation: "Sophie had been brought up so straight-laced that she possessed no very exact notion of how babies were made in the first place or born in the second until she learnt from personal and startling experience."

As such passages make evident, Patrick O'Brian's elegant prose demands a certain attentiveness (as well as a liking for a slight but pervasive irony). Consider one mark of his narrative virtuosity: the penchant for leaving things out, for building up to an important action -- a naval encounter, a trip into the interior to study the local fauna -- and then simply skipping over it. Usually the reader must fill in the details after the fact from conversations or consequences. At one point in The Commodore Stephen learns that his daughter and household are in grave danger. But does O'Brian detail Stephen's angst? Not at all. Instead he focuses on the exhilaration of sailing up the Thames to the rescue in a fast Baltimore clipper. Among myriad other reasons, O'Brian's often quite long novels never pall because he presents the scenes you don't expect rather than those you do.

If I have spoken so much here about O'Brian's work in general, it is not because The Commodore is in any serious way unsuccessful. In fact, it is thoroughly engrossing, albeit a somewhat melancholy and autumnal book, replete with insider allusions to earlier exploits and unusually rich in coincidence (especially at its end). In essence, the novel relates what happens after Jack and Stephen return from their long voyage of several years in the Pacific. Many pages are domestic, the marital trials that await our heroes mirroring the courtship agonies of previous volumes. Jack and Sophie, for instance, suffer from mutual suspicion and jealousy; Stephen discovers that Diana has again disappeared, mainly because of guilt over their beautiful but seemingly retarded daughter; the enemies of Sir Joseph Blaine are threatening both the spymaster and his agents; the admiralty is playing fast and loose with their promises and ship assignments. Eventually, Jack is given command of a small squadron and sent to the African coast to harass slavers and later to forestall a French plan to transport men and arms to Ireland. Along the way, Stephen meets with undercover operatives, chews too much coca, feels tempted into an affair with an attractive woman naturalist and falls prey to a dangerous illness.

In short, there is no lack of action, but much of it can be properly savored only if one possesses some acquaintance with what has gone before. Jack, Stephen, Sophie and Diana, as well as the sailors Killick, Babbington, Bonden, Pullings and Heneage Dundas, share a multitude of past experiences. No one interested in reading about them will wish to start with The Commodore. Those who have followed the saga so far need no further enticement: Aubrey and Maturin are like family -- you want to know everything that happens to them. In a just world, these wonderful characters will enjoy a great many more years of philosophic discussion, domestic upset and high-seas adventure. Michael Dirda is a writer and editor for Book World.