To read Peter Ackroyd’s Thames: The Biography is to cruise the storied river in the company of an erudite guide, one who knows every bend, island, and town along its 215 miles from its source in Gloucestershire to its mouth in the North Sea. But like so many docents, Ackroyd says far too much, dumping on his readers every name, date, fact and rumor.

There’s natural history here, English history, geology, economics, biology and botany; there are bits of folklore, maps, illustrations, and a 40-page coda with etymologies and details that somehow didn’t make the cut. Awash in this perpetual high tide of information and digression, some readers are likely to nap every so often only to open their eyes for the really good stuff they wanted in the first place.

And there is good stuff aplenty here. As we might expect from the author of London: The Biography, Albion, and Shakespeare: The Biography, Ackroyd is one very informed writer. One of the delightful features of this “biography” is the way it uses England’s cultural history as a way of getting at the essence of the Thames. It’s no surprise that, as the author of books on Thomas More, Dickens, Blake, Turner and Chaucer, not to mention two volumes of poetry and some dozen novels, Ackroyd uses literature to put the river in a broader context.

His chapter on “The Song of the River” begins with the notion that the Thames’ “endless melody may be glimpsed in all the poetical legends and myths of the river.” We hear from a who’s who of writers, from the 14th century’s John Gower, up through Chaucer, Shakespeare, Milton, Pope and Wordsworth.

From the beautiful and stirring to the gruesome, there’s something here for everyone. “There is a curious connection between the Thames and severed heads,” Ackroyd claims, adding that “heads were deposited in the river from the earliest times.” He’s particularly keen on dredging up and examining all sorts of things that have been thrown into the Thames or buried in it by Britons, Romans, Saxons, Danes, Normans and by centuries of good old Englishmen. Then, too, Ackroyd has an art historian’s way of examining artifacts — weapons, statues, jewelry — and of talking about painted and etched representations of the river. Thames is the grandest smorgasbord ever devoted to one element of topography.

Among the items spread before us, however, are observations that apply to any river, anywhere, along with New Age snippets (“We come from, and return to, the water”), and simply irrelevant details — about the Nile, Nero, Poseidon, Scandinavian myth. Some readers will want it all — Plutarch, data on regattas, Isis, the derivation of the word “chalk,” and so on. Most, I think, will drift in and out, like the tides on the Thames itself.

antjlewis@yahoo.com