Although I am not an expert, I have read numerous books on the subject of Byzantium, in Greek and in English, varying from school textbooks, to the widely accepted books of famous scholars like Vasiliev and Ostrogorski. I must admit that John Julius Norwich in his trilogy "Byzantium", is succesful in producing by far the most intriguing and "easy" byzantine history books that I have read. Once started, it is very diffcult to lay the book back on the table. This is partly due to the fascinating nature of Byzantine history, but also to the wonderful writing style of John Julius Norwich; he not only has a deep knowledge of the subject, but he is also a great writer. His book conveys the full scale of historical events and characters of the history of a christian empire born out of the ashes of the Roman state.
Founded in 330, a year that marks the glorious opening of the "city of cities", Constantinople, Byzantine history ends with the sacking and destruction of this very same city by the turkish hords in 1453, that has since stood on the Bosporus only to remind us of its past greatness. During its 1123 years, the empire progressed to an unforeseen glory and wealth in all aspects of human activity, and has laid the foundation of Europe and the Western civilization in general.
This first book covers the first four centuries, starting from the first Christian emperor, Constantine the Great, the founder of Constantinople, and ends with Irene the Athenian, that ruled in the East during the days of Charlemagne in the West.
Dates and important events are noted in the headers of every odd page, making random reference very easy. The book comes in its usual poor paperback quality.
If you decide to buy this book, which I personnaly strongly recommend, I believe that you'd better buy all three books of Norwich's "Byzantium" series together. They are definitely worth it.