Aubrey faces life off the Navy List, as the captain of a letter of marque, finding heart to endure and train yet another ship's crew, but of volunteers, with no Marines aboard.
[1] The two principal characters, "bluff, hearty Aubrey and reedy, intellectual Maturin", return for an exciting story with accurate historical depictions.
He runs the Surprise on Royal Navy lines, including regular pay to the men, in addition to any prizes they might take.
He is supported by his crew of old Surprises, privateers and smugglers, the latter groups recruited in Shelmerston, on the western coast of England.
The downfall of the traitors Wray and Ledward restores order in British intelligence circles, returning Sir Joseph Blaine to his position in the Admiralty.
Blaine tells Maturin of the frigate Diane, a French navy ship ready to voyage to South America.
Aubrey plans the attack at night in ship's boats, cooperating with the Navy, specifically William Babbington of HMS Tartarus, who has made post Captain, thus removing pressure on him to take credit for success.
They carry Maturin out to the ship in style, accompanied by Colonel Jagiello's escort, and Diana embarks with him for home.
Ledward and Wray were exposed as spies for France by Duhamel, who returns the valued diamond, the Blue Peter, to Maturin as was long ago promised.
Kirkus Reviews finds the novel "authentic and engaging", and O'Brian "a brilliant stylist of sea-historicals".
The personal worries of Aubrey (his family's finances are in shambles at the start) and Maturin (who wants to win back his estranged wife) "add fiber to the characterizations".
This review notes Aubrey's triumph over the French in taking their frigate and all ships in one harbor, and his deceptions for the enemy.
As to O'Brian's writing, they found "his every sentence sensuous and emerging from saltwater as naturally as the leap of a flying fish.
"[1] Library Journal finds this long-awaited sequel (in the US) to be an "exciting sea story with good character development.
"[2] O'Brian "created two wonderfully contrasting characters in bluff, hearty Aubrey and reedy, intellectual Maturin.
"[3] They proffer the notion that "If Jane Austen wrote Royal Navy yarns, they might read like this" novel.
[3] Richard Snow cites a scene in this novel when the two seek and find the "true line" of a piece by Mozart as illustrating that the "only intellectual common ground the friendship enjoys is the mutual love of music" in an article about the re-issue of the series by W W Norton.
He inquires about the coca or cuca leaf from Peru, which he learned about in a previous mission, detailed in The Far Side of the World and the apothecary replies, "It is said to dissolve the gross humours and do away with appetite."
In August 1990, The Letter of Marque was the first of the series novels to be issued by W W Norton in hardback and in paperback in the US, two years after the first edition was published in the UK, and it was an instant success.
[7] This drew a new, large audience to the series, and new attention to the author, as well as positive reviews such as in Library Journal, Publishers Weekly, and one by Richard Snow in the New York Times shown above.