When Diane Aziz drives her oldest son, Walter, from Los Angeles to college at UC Berkeley, it will be her last parental act before falling into a deep depression. A single mother who maintains a wishful belief that her children can attain all the things she hasn't, she's worked hard to secure their future in caste drive 1980s Los Angeles, gaining them illegal entry to an affluent public school. When she enters a state hospital, her closest friend tries to keep the children safe and their mother's dreams for them alive.

At Berkeley, Walter discovers a passion for architecture just as he realizes his life as a student may need to end for lack of funds. Back home in LA, his sister, Lina, who works in an ice-cream parlor while her wealthy classmates are preparing for Ivy league schools, wages a high stakes gamble to go there with them. And Donny, the little brother everybody loves, begins to hide in plain sight, coding, gaming, and drifting towards a life on the beach, where he falls into an escalating relationship with drugs.

Moving from Berkeley and Los Angeles to New York and back again, this is a story about one family trying to navigate the crisis of their lives, a crisis many know first-hand in their own families or in those of their neighbors. A resonant novel about family and duty and the attendant struggles that come when a parent falls ill, Commitment honors the spirit of fragile, imperfect mothers and the under-chronicled significance of friends, in determining the lives of our children left on their own. With Commitment, Mona Simpson, one of the foremost chroniclers of the American family in our time, has written her most important and unforgettable novel.