This book was fascinating and frustrating; fascinating, because its author Guy Halsall had done his homework, studying the sparse historical record -- and increasingly burgeoning archeological record -- of Britain roughly from the 4th through 7th centuries (of the common era) and frustrating because of the odd structure of the book and his style of writing. He is overly fond of the verb "to be" and of the passive construction.
That said, he provides an important window on what he suggests could be dubbed an "interhistoric" period, between the relatively well-documented era of Roman dominance of Britain and the decently documented concluding centuries of the first millennium (of the current era).
In the preface, this self-confessed "romantic Arthurian agnostic" acknowledges that he wishes King Arthur "had existed," but regrets "that there is no evidence--at any rate none admissible in any serious 'court of history'--that he ever did so." He also reminds his readers that it is "impossible to prove . . . that he didn't exist".
Halsall goes through the references Arthur, noting how few there are in the five centuries after the time when the celebrated king supposedly flourished. Only after Geoffrey of Monmouth published his celebrated Historia Regum Britanniae ("History of the Kings of Britain") in Twelfth Century did Arthurian romances become commonplace, that is, in the literature that survives today. (Who knows what stories the largely illiterate populations of Britain told as Germanic kingdoms dominated where once Rome ruled.)
After going through the basic version of Arthur's legend and supplying the "traditional" historical context--that Arthur rose to power rallying the indigenous British (i.e., the Celts who lived on the island before, during and immediately after the Roman occupation) population against the (Anglo-)Saxon invasions--Halsall considers the archeological record and offers an alternative view. He suggests that instead of a conflict Britons and Saxons in the "interhistoric" period, the situation was more complex in post-(Roman) imperial Britain. It wasn't as simple as a British king holding off the Saxons for a generation. Different realms had different degrees of influence in different eras, with even the Franks (possibly) holding sovereignty for a period of time.
Those expecting a book with much information about King Arthur (or considered speculation about his actual existence or reflection on the appeal of tales about him and his court) will be disappointed. Instead, Halsall spends the last two-thirds of the book studying the era in which the legendary king allegedly flourished (and all but ignoring the book's eponymous sovereign). And that is when he is at his best.
He studies the archeological record and dips into his knowledge about the better-documented Merovingian era in France, as Frankish invaders replaced Roman rulers in the one-time province of Gaul. And this particularly fascinated one who has considered the the historical background of Arthur and studied that of the Beowulf-poet.
Throughout, he is careful to make clear that he is offering his own reading. He doesn't presume to prove what, giving the surviving record, cannot be known. Nor does he dismiss those of us who love the legends.
Those legends of Arthur, like those of Troy, each fascinated an era roughly half a millennium after the king (supposedly) reigned and the ancient city (allegedly) fell. And we continue to read books, watch movies (and TV shows) about them. While archeological evidence suggests that there was a Troy and that a great battle was fought there, we will never be able to prove if that battle was the great epoch-defining conflict that Homer describes.
We have even less evidence to go on as we try to discover the truth about Arthur. But, in the end, that doesn't matter. The stories are good ones. And they continue to draw our attention.
Perhaps another writer will explore just why that is (if one has not done so already). But, until he (or she) does, let's just enjoy the stories, delighting in the characters, savoring the romance and appreciating the sorcery.
It's not just a history that makes a good story. The supernatural elements help the legends of King Arthur stand the test of time.
All the said, Halsall has written an important book about the era when that noble prince supposedly flourished. And gives us some insight into a turbulent time about which we know so little.