What is the author's style in Boss: Richard J. Daley of Chicago by Mike Royko?

The story is written by renowned Chicago newsman, Mike Royko. He bases his story on news reports of the day and personal accounts by those involved in politics during Daley's reign as Mayor of Chicago. As a writer, he gleans and assumes some attitudes from the many tales of Daley's power and authority. A portion of the story must be attributed to legend and myth. But when the same stories are told time after time from different sources, one can assume there is more than a measure of truth to the myths and legends. There are episodes in the book in which Royko is repeating conversations Daley had with others. While he depends on the witness of those present or others to whom the conversations were retold to, his research efforts and storytelling have produced a story that is cogent, detailed and complete.