Some common reasons include: 

1. Offensive language or content: Books containing profanity, racial slurs, or explicit descriptions of violence or sexuality may be challanged or banned due to concerns about their appropriateness for certain age groups or audiences. 

2. Sexually explicit material: Books that contain explicit sexual content, including descriptions of sexual acts or themes, may be banned or challenged, particularly in schools or libraries catering to young readers.  

3. Religious or Political Views: Books that challenge or question religious or political beliefs, or that present alternative perspectives on sensitive topics, may face censorship from groups or individuals who find their ideas objectionable or threatening. 

4. Sensitive themes: Books dealing with sensitive topics such as racism, sexism, homophobia, mental illness, or drug abuse may be banned or challenged if their portrayal is deemed offensive or inappropriate by certain individuals or groups. 

5. Violence or graphic content: Books containing graphic depictions of violence, particularly towards children or animals, may be banned or challenged due to concerns about their potential negative impact on readers. 

6. Social Controversy: Books that address controversial social issues or challenge prevailing norms or values may be banned due to an attempt to suppress dissenting viewpoints or maintain the status quo. 

7. Age appropriateness: Books may be banned if they are deemed unsuitable for a particular age group or developmental stage, either due to there content or level of complexity.

8. Fear of influence: Some individuals or groupss may seek to ban books out of a fear that their ideas or themes could influence readers in a negative way, such as promoting violence, drug abuse, or disobedience. 

Photos of banned books at our library here at UD: