The "Dark Ages" - roughly from the decline of the Roman Empire in the fifth century to Charlemagne - is a misnomer.
Yes, the barbarians dismembered the Western Roman Empire and learning and culture declined. Except for the Papacy and the Catholic Church, the universal institutions withered away. But Roman culture never entirely disappeared. Rather, it merged harmoniously (and often violently) with the Teutonic culture of the ruling barbarian tribes. For three centuries, Europe experienced not so much a collapse as a transformation, which culminated in the person and empire of Charlemagne.
British historian H. St. L. B. Moss (a very British byline, I might add), although writing from a secular and materialistic point of view, wrote an excellent summary of this important period of European history, which he dates from the death of Emperor Theodosius the Great in 395 A.D. to the death of Charlemagne in 814 A.D.
Part I of his book begins with a description of the culture and social structures of the Roman Empire and the barbarians. In Part II he describes the Byzantines and especially Justinian II's influence on Italy and the West. In Part III he treats Islam, its faith, conquest, and culture. Part IV is about the age of Charlemagne, the Franks, their relations with the Papacy, the beginning of the Papal States, and the person and character of Charlemagne himself.
Moss touches upon every important aspect of this transformation: law, politics, religion, learning, language, literature, ethnic changes, social institutions, although he focuses more on cultural changes than political or religious ones. An exception to this is Byzantium, or the Eastern Roman Empire, which looms large in his narrative.
His book is well-written, well-researched, and fairly balanced for a 20th-century historian.
Of course, everyone has their biases. As he is English and a modern historian, he does recognize the importance of Catholicism and the Papacy in this crucial phase of European history but tends to understate or minimize them. He considers Christianity as more an observer than an active agent in these great cultural changes. He also tends to minimize the destruction wrought by the Islamic conquest of the Levant and North Africa, while understating Christian victories over Islam, such as the Battle of Poitiers in 732: "This battle has become a symbol of the salvation of Western Christendom from the infidel terror, and its legendary fame is not unjustified. But in fact the force of the invasion was spent, and it is doubtful whether any permanent conquest of southern France would have been possible." (p. 156) Try telling that to an 8th century Christian in Syria or Spain.
Overall, "The Birth of the Middle Ages, 395-814" is an excellent summary of early Medieval European history. It helps to dispel the popular myth, invented by Petrarch in the Renaissance, that the era after the fall of the Roman Empire was nothing but an "age of darkness."