What is the main conflict in Palace Walk by Naguib Mahfouz?

Ahmad Abd al-Jawad is a domestic tyrant, demanding instant and absolute obedience to a household standard that few Muslims follow. Pious wife Amina prides herself on being submissive and supportive. She prays constantly for her family's welfare. She alone knows of his other side: nightly rounds of drinking and sex. Outsiders see Ahmad as the life of any party, musical and generous. A religious man, Ahmad depends on God's mercy.