Simon Schama is best known to American audiences as the snarky British host of the BBC's epic 15-part series A History of Britain. But the expatriate professor of art history at Columbia University is much more than a Simon Cowell for the History Channel set: His books on the Dutch Republic and the French Revolution are landmarks in their field. Compared with this earlier work, however, Schama's latest book, Rough Crossings: Britain, the Slaves, and the American Revolution (Ecco, 478 pages, $29.95), is a muddle to rival the siege of Yorktown.

From its prologue, Rough Crossings is, as its title suggests, anything but smooth sailing: Schama's sense of narrative, usually crisp as a regiment of redcoats on parade, is limp and disjointed, and the book's editing seems slapdash, as if it were heavily revised from the U.K. edition, which was published in Britain almost a year ago as part of a seven-figure deal with BBC Books. And Schama's premise suffers, as well: At the outset, he argues for a new perspective on the American Revolution, proposing that Britain's promise to free American slaves loyal to the crown—or, worse yet, to arm them against their white masters—may have done more to mobilize Southern colonies to join the War of Independence than taxation without representation did to ignite New England. But then Schama digresses from this intriguing argument to catalog Britain's blunders in executing the war, which are sometimes only tangentially related to the tens of thousands of slaves who fled to the British in hopes of winning their freedom. About halfway through the book, Schama changes course again to recount the British abolitionist movement, which only peripherally concerned the plight of American slaves and focused primarily on eradicating the West Indies slave trade, a subject already treated more thoroughly in Adam Hochschild's Bury the Chains.

Schama's flair for the pithy anecdote flashes briefly throughout Rough Crossings, as when Gen. George Washington uncharacteristically embroils himself in an unpopular scheme to hang a captured British noble for a murder he didn't commit. But such moments are all too few. As the defeated British pack off their slave dependents to doomed colonies, first in Nova Scotia then in Sierra Leone, it's unclear whether Schama means to portray his countrymen as liberators or betrayers. In his drive to make history palatable to the television masses, Schama the celebrity broadcaster seems in danger of crowding out Schama the serious historian.

Simon Schama appears at Powell's City of Books, 1005 W Burnside St., 228-4651. 7:30 pm Wednesday, May 17. Free.