This is an entertaining, informative, well-written, funny and captivating account of the Byzantine empire from Constantine up to the accession of Alexius Comnenus.
It is not as detailed as Professor Bury's or Ostrogorskji's, but much more lively, and if you need a spark for your interest in the history of medieval eastern mediterranean this is the book for you. Characters are described with the finest touch, and the accounts of plots and battles are memorable.
I could not put it down.
What are the lows, then? First, the maps included are simply useless: many of the places quoted in the narration are not on them and sometimes it is difficult to understand how some battles really went; second, little attention is paid to the countries outside the capital: Greece is completely neglected, for example, as it is Anatolia: but after all, the book is titled Byzantium and thus it is centered on the town itself; finally, little account is given of the ideas and the philosophies which were popular at the time, and of the arts in general. However, these are information which you can easily find in a standard book on medieval history: where you will never find, on the other hand, the sheer pleasure of reading pages such as those written by Norwich.