This is another masterpiece of popular history (although based on serious research and rigorous)by Julius Norwich.
The book is actually the final volume of the Byzantium trilogy by the same author, which covers all the over 1000 years of history of the Byzantine empire.
Readers who have already read the previous volumes already know how enjoyable and informative they are: the third volume adds to the virtues of the first two parts a tragic - at times pathetic - tone: this is the history of an agony, starting with the fall of the Comneni dinasty and extending over two centuries, during which the Byzantine empire is progressively reduced in its size, depleted of its riches, divided by internal strifes. It is a sad history indeed: and Julius Norwich is a master in striking a perfect balance between the need to give a serious account of a decline which has manifold causes, and that of keeping the reader involved in the narration.
He succeeds perfectly: at the end of the book you will know why Byzantium fell, and at the same you will feel sorry for it, after having ventured into the captivating account of the last siege by Mehmet the Conqueror (although this part of the book is basically a summary of Professor Runciman's previous work, as acknowledged by Norwich himself).
Finally, as suggested by other reviewers, I would recommend if possible NOT to buy the one-volume synopsis of Norwich's trilogy: don't be put off by the size of the three volumes, they are thoroughly enjoyable! Go for the big read!