I tend to read batches of books on themes, and this year one of my themes was preaching/speaking. I read several books by prominent pastors and professors about how to prepare and preach a Biblical sermon. The most popular books on preaching are often those by famous preachers, men that we want to be like and imitate. Often these pastors have large platforms and impressive ministries, with a built in base to sell books. Their public ministry seems to make them an expert in their field.