Complex sentence: Ibn Abd-el-Hakem (d.870 or 871) was an Egyptian who wrote the "History of the Conquest of Egypt and North Africa and Spain" which is invaluable as the earliest Arab account of the Islamic conquests of those countries.
Split into simpler sentences: Ibn Abd-el-Hakem (d.870 or 871) was an Egyptian who wrote the "History of the Conquest of Egypt and North Africa and Spain". His work is invaluable as the earliest Arab account of the Islamic conquests of those countries.