What do we learn about Mariam's early experiences of marriage?

The story of Mariam's life is a tragic one in Khalid Hosseini's A Thousand Splendid Suns. She is the illegitimate child of a rich man and a woman who was his servant. She is raised by her mother, though her father occasionally visits; she cannot live with him, since he has three legitimate wives with their own children. Mariam's mother eventually commits suicide, and Mariam lives with her father briefly.
He quickly arranges her marriage to an older man, a widower named Rasheed who owns a shoe shop and has a house. Mariam protests, but she becomes his wife when she is only fifteen. Mariam must learn to serve her husband, to clean the home and cook his meals to his preferences. She must be subservient to him and forfeit her autonomy. She cannot continue her education or work. She is expected to bear his children. Mariam does become pregnant but loses the child. She never ends up producing a child. The early years of Mariam's marriage are lonely. She is also physically abused by her husband and loses hope that her life will ever improve.
Eventually, Rasheed brings Laila into the home, making her his second wife. She has a daughter, Aziza, within the first year of the marriage; the girl is actually the child of Laila's true love Tariq. She later has a son with Rasheed named Zalmai. The introduction of Laila to the family eases the relationship between Mariam and Rasheed somewhat, as he pays more attention to Laila, but he is abusive to Mariam and insults her constantly. Rasheed physically abuses both of his wives throughout their marriages. Late in the novel, Mariam kills Rasheed as he tries to kill Laila. Mariam is put to death for the crime, after she turns herself in to protect Laila and allow her to run away with Tariq and her children.