Marrin is an American historian, history professor, and author of over 40 history books for children and young adults. He was born and raised in New York, where he attended City College of New York, Yeshiva University, and Columbia University. He was a public school teacher before serving as chair of the History Department of Yeshiva University.

Marrin is an acclaimed writer of history for children but has made it a point not to write down to his young readers. He has been praised for his fresh and relatable writing style, which engages readers of all age levels. According to his biography, Marrin became interested in telling history stories as a secondary school teacher in the South Bronx. After publishing many scholarly works, Marrin returned to engaging kids with history.

During his doctoral studies at Columbia University, Marrin focused on the concept of liberty under law. This has guided his work, including books about the Mexican War, the Vietnam War, pirates, and the experiences of Indigenous peoples of North America in the mid-19th century. Flesh and Blood So Cheap follows suit, highlighting the intersection of human rights, power, money, and labor law in early 20th-century New York City.