The history and archaeology of Britain in the 'Dark Ages'; a bit out dated now, but still the best overview of Britain in this popular historical period. Features everything from housing, warfare and society to source material and techniques of archaeological excavation. This book was first written in the 1970s and was updated in 1989, and is written by one of the finest 'Arthurian' historians known. Arthur's Britain is a far better read than John Morris' Age of Arthur, which takes a less critical use of all available sources (regardless of their value) and presents a rather more unliely scenario for post-Roman Britain.
Over thirty years after it was first compiled, and 15 since it was last updated, Leslie Alcock's Arthur's Britain remains the most useful guide to this popular period of British history. New discoveries fill in more of the blanks with every passing year, and new theories regarding Arthur and the political situation in post-Roman Britain have emerged since this book was first written, but even so, it still comes highly recommended to anyone wishing for a balanced view of what might have happened. For me, Arthur's Britain still surpasses any other readily-available book on the British early medieval period.