A contributor's expertise and credentials should relate to your subject. A credible book author might:

• Have a degree in this subject
• Study or do research on this topic
• Work in a related field
• Write about this topic regularly
• Have first-hand knowledge
• Have participated in, or observed, events and people

Every author has opinions and a worldview that shape his or her treatment of a subject. As you read the book, ask yourself how the author's views and affiliations might affect the presentation or omission of information.