It is definitely a fair statement to say that To Kill a Mockingbird is a book about prejudice and injustice.
Lee tells the story through the eyes of young Scout Finch, who sees many different kinds of prejudice during the course of the novel. A great example of this is the fact that despite being an obvious tomboy, Scout is pushed by various characters to be more ladylike. This is a classic example of gender stereotyping, which is a form of sexism. Sexism, in turn, is a type of prejudice.
Looking to the obvious theme of racism as a type of prejudice, we must consider the fact that Tom Robinson is found guilty of rape. Despite evidence presented by Atticus which proves that he could not have raped Mayella Ewell, there is an assumption that because he is Black, he must be guilty. Racism is also seen in reverse when Calpurnia takes Jem and Scout to church. While most congregants welcome them warmly, a lady named Lula wants to know why Calpurnia is “bringin’ white chillun” to their church.
In terms of injustice, Lee portrays this theme beautifully through the unfair trial of Tom Robinson. Thanks to the false testimony of Bob and Mayella Ewell, Tom is wrongly found guilty. To add another layer of injustice, Tom is fatally shot while attempting to escape from prison, meaning that he could never be granted justice in an appeal court.
In addition, Tom is not the only victim of injustice in this novel. Consider the situation that Boo Radley is in, with rumors having been spread around town about him for years. These rumors lead people to unjustly believe that he is a misfit, but he winds up being the hero who saves Jem and Scout from Bob Ewell.