Heart Eater traces the author's childhood and how she went from being a nameless, abandoned nine-month-old baby in Seoul, South Korea to, as an adult, becoming an award-winning Asian American author who writes in multiple genres. The book is made of short essays, or "field notes," that explore moments and experiences in the author's life that made her pay extra attention to the words being used.

Each titled "field note" memorializes and reflects on encounters with language regarding race, ethnicity, migration, kinship, citizenship, gender, class, that would eventually become the foundation of the kind of writer she would become. Her public school education, her upbringing in the Roman Catholic Church, and nearly everything she experienced during her American childhood contributed to her ability to answer the question that has obsessed her since she was young, "What does it mean to be American?"