Michael Psellus, a court official in Constantinople, witnessed Byzantium's rapid military decline after it reached its peak at the death of Basil II. He paints a vivid picture of how bickering and scheming Court officials, combined with the astonishing succession of over 8 Emperors in 36 years after Michael IV (all fairly mediocre; in terms of their competence at least) led to the destruction of Byzantium's ambition and former reality of being a world power at the battle of Manzikert 1071.
This title should not present too many problems for those without much knowledge of the period in Byzantium as Psellus's text is nicely self contained, though a grasp of the general situation outside of the Empire may be useful to the reader. Byzantine idiom, such as Porphyrogenitus etc... are explained in the introduction and footnotes.
Psellus writes with first hand knowledge and erudition, the introduction is great and I heartily recommend his Chronographia to anyone interested in this period.