The book begins, not on the deck of a ship or in the depths of some squalid seaside tavern, but in a home in suburban London, where an elderly shipwreck researcher is downsizing.

Writer, editor and shipwreck hunter Sean Kingsley was helping fellow wreck hunter Rex Cowan clean out his home before moving when the subject of conversation turned to pirates. Cowan dug out the research done by his late wife, Zelide Cowan, who back in 1978 had unearthed a letter ostensibly from the pirate Henry Avery that had been misfiled for centuries in a Scottish archive. The most startling thing about the letter was that it had been written four years after Avery had disappeared from public view.

Avery, of course, was the most successful pirate of all time, the spark that lit the fuse and inspired later generations of pirates such as Blackbeard, William Kidd, "Calico Jack" Rackham and the rest. The reason for his renown was a single successful raid on a Mughal ship off the coast of India in 1695, taking a fortune the likes of which had never been seen before or since.

But, while many famous pirates ended their careers in battle or at the end of a rope, Avery simply vanished ... and rumors about his ultimate fate, for good or ill, were never proven.

The letter found by Zelide Cowan was written partially in code by "Avery the Pirate" and seems to shed new light on his later life. Although its origins have not been proven, Kingsley makes a persuasive argument for its legitimacy ... and in The Pirate King: The Strange Adventures of Henry Avery & the Birth of the Golden Age of Piracy, he and Cowan tie Avery's later life to early 18th-century espionage and link his activities to Daniel Defoe -- nee Daniel Foe, the author of Robinson Crusoe and Moll Flanders and, less well known to many, a master spy for the English crown -- and Thomas Tenison, the rabidly anti-French and anti-Catholic Archbishop of Canterbury.

Much of the book is devoted to retelling the life and times of Avery and, to a slightly lesser extent, Defoe. It's an interesting history, and readers with a passion for the period, as well as general nautical and political themes, should enjoy it. Kingsley tells his story thoroughly and with an eye for detail that makes it hard not to enjoy.

Less interesting are some snippets that are presented as history but are actually conjecture on the part of the author. For instance, one chapter recreates a convivial meeting and conversation between Avery and Defoe in a tavern that, if it happened, certainly was never recorded in the detail that the author claims to know. Also, the two men share an imperceptible nod across the crowd at the public execution of several of Avery's men -- and, again, if the two men were even present, that exchange is simply guesswork.

The amount of supposition only increases as the book moves into later years, when Defoe took a more active role in matters of politics, intrigue and counter-insurrection. While much of his involvement is a matter of history, Avery's participation is mere speculation. However, Kingsley treats the notorious pirate's activities -- when he "came in from the cold" and spent his life in loyal service to King William III, Queen Anne and King George I -- as a matter of public record.

A less than careful reader might believe this book is an actual history, rather than a plausible series of assumptions and educated guesses. It wouldn't have taken too many narrative liberties to cross the line into historical fiction.

Don't get me wrong, The Pirate King is a good book and it's worth reading. Where the facts are known, Kingsley presents them effectively. Just take the speculative portions with a grain of sea salt.