On 14 July 1958, when Colonel Abdul Karim Qassim took control of the Kingdom of Iraq by a coup d'etat, the Royal family was ordered to leave their Palace in Baghdad. The group consisted of King Faisal II; Crown Prince 'Abd al-Ilah; Princess Hiyam, Abdul Ilah's wife; Princess Nafeesa, Abdul Ilah�s mother, Princess Abadiya, the king�s aunt; and several servants.
When all of them had congregated in the courtyard they were told to turn towards the Palace wall, they were all then executed by firing squad under the command of Captain Abdus Sattar As Sab, a member of the coup d'�tat led by Colonel Abdul Karim Qassim. Nuri as-Said, the Prime Minister of the Kingdom of Iraq, was subsequently killed by Qassim's supporters on 15 July, 1958.
I haven't heard of the book you mention, but maybe you read something (generally unrelated) by Jean Sasson?
http://www.jeansasson.com/princess_trilogy.htm