This tome in the Oxford History of England series was originally presented as the final few chapters in a much longer work about Roman Britain, and now offered as a separate volume. The current edition is much less hoary than others in the series (it was published in 1986). It covers the very darkest of the Dark Ages (my favorite part), from the first appearance of the Angles and Saxons in Britain in the fifth century to the establishment of the earliest Anglo-Saxon kingdoms in the seventh.
With scant contemporary literature, and archaeological remains not much better, much has to be pieced together from studies of landforms. To understand early Anglo-Saxon Britain, you have to walk it - some of the bones of this landscape can still be found, though recent building has obscured much. From this work, though, I learned a great deal: for example, that the Anglo-Saxon invasion was probably more gradual than we imagine. Quite a few Anglo-Saxons were probably settled as foederati on the eastern shores of Roman Britain as they were in other parts of the Imperial periphery. The system of Roman coastal defences known as the 'Saxon Shore' wasn't to defend against any Saxon incursion, but was manned by Saxons to control the incursion of any more of them.
Some essential questions, though, remain unanswered - for example, why the populous and civilized society of Roman Britain collapsed to almost nothing within a century, leaving an empty land with hardly a scrap of literature or native tradition. I shall revisit this book often.