You do not need to read an entire book cover to cover in order to use it as a source in your research assignment.
Look at the table of contents to see if there is a chapter that addresses your narrower aspect of a broader topic covered in a book. For example: Is there a chapter about Ohio's response to the opioid epidemic in a book about the broader national response?
Or you can use the book's index to see which specific pages a book contain information about your topic and read only those pages. (For example: Perhaps a book about the opioid epidemic includes information about Ohio drug courts on pages 72-75).