Just Mercy, Bryan Stevenson's memoir, depicts the story of Stevenson's establishment of his work in law and his founding of the Equal Justice Initiative, which seeks to provide just treatment for all caught up in the court system. The book flows chronologically through Stevenson's beginning years as a lawyer during the 1980s and 1990s. Although several cases are discussed within the book, each pointing to the unjust treatment of people of color, people of low socioeconomic status, and people with mental health problems by the courts, the book centers mainly on the case of Walter McMillian. McMillian was condemned for killing a white woman in his hometown of Monroeville, Alabama, with very little prosecuting evidence and a lot of prejudice, until Stevenson's work on the case was able to exonerate him. This story serves as a backbone for the entire narrative so well because it includes many elements that are obviously important to Stevenson's work, including the existence of racial bias, the plight of the less fortunate when they are faced with the court system, and the responsibility of all to provide merciful justice to those people. Since taking on McMillian's case, Stevenson has continued to work within the Equal Justice Initiative to exonerate others who have been falsely convicted.

Just Mercy is a non-fiction book that acts as a memoir for Bryan Stevenson. It focuses on his creation of the Equal Justice Institute, an organization created to provide legal representation to the individuals with the greatest need for help. Stevenson tells his story about his time with the Institute through discussions of several of his cases, each of which demonstrate a failing of the criminal justice system. The case of Walter McMillian is among the most egregious as Stevenson uncovers evidence that the local police may have fabricated witness testimony in order to secure the conviction and, even after bringing this to light, the prosecutor is reluctant to reexamine the case.

Stevenson also places a significant emphasis on the issue of over-punishment. He discusses this with regard to children who have been sentenced to life sentences before the age of 18 and with regard to a client who was suffering mental problems as a result of his life. Overall, Stevenson's book serves double duty as both a memoir of his time creating the Equal Justice Institute and as a book focusing on the failings of the criminal justice system, especially around the issue of race.

Bryan Stevenson's book discusses the ramifications of the death penalty, the treatment of juveniles in prison, and the plight of black men within the American justice system.

The book begins by drawing attention to the murder of Ronda Morrison, an eighteen year old white woman from Monroe County, Alabama. A black man, Walter McMillian, was implicated in her murder. Stevenson compares McMillian to Tom Robinson, the iconic black protagonist in Harper Lee's To Kill A Mockingbird. Even though McMillian was never at the scene of the crime, he is pronounced guilty and sentenced to death.

Stevenson concludes that McMillian's race sealed his fate, despite the lack of evidence connecting him to Morrison's death. Stevenson also documents the fate of military veterans who suffer from debilitating medical conditions upon their return from war. He recounts the case of Herbert Duncan, a Vietnam War veteran who was sentenced to death for his crimes in Alabama.

Stevenson later takes on McMillian's case, and he is contacted by Darnell Houston, who warns him that one of the eyewitnesses in McMillian's case lied under oath. Despite this, the Alabama Court of Criminal Appeals denies McMillian's appeal, and his death row sentence stands.

Throughout the book, Stevenson documents his efforts on behalf of impoverished citizens caught in the bureaucracy of a discriminatory justice system. He cites cases in Florida and California, where juveniles were sentenced to death or to life imprisonment without parole for non-homicide crimes. In 2010, his efforts result in the Supreme Court ruling against life imprisonment without parole for children convicted of non-homicide crimes. Stevenson also works on behalf of women and the mentally ill within the American justice system.