When summarizing a nonfiction book you must include information as to what the book is about without revealing all of the intricate details, a summary is meant to provide an overview therefore in order to write a nonfiction book summary you have to read the book or whatever you’re summarizing obtain a general idea of what it’s about and state the relevant pieces of information regarding the content in chronological order.. Hope this helps good luck :)
Since the author wrote the story and is in charge of things going in that particular book, it has a full knowledge of all characters, rather than just one character.
