The last volume of The World Book Encyclopedia has something called a Research Guide. This is a wonderful guide to communication and includes the following short help sections:
You should read through this source carefully. It is filled with good tips. In the area of book reports it covers the following areas:
Read through this material.
In addition, I would make these suggestions.
The important part of a book report is YOUR reaction to the book. You should choose one or two aspects of the book's story and discuss them in the light of what you thought, your past experiences and ideas.
If an extensive report is expected, you might also want to look up what other critics have said about the book. You could put that material at the beginning, rather like a literature review. Or, you could place other critics after your analysis and compare their reactions to your own.
If the book is nonfiction, don't forget to discuss the validity of the information presented. Is the author biased. Is the information given biased, skewed, verifiable?