Using academic/scholarly books on your topic can be a great way of gaining introductory information on a global health issue you are examining. Unlike journal articles, books do a better job of providing an overview of a topic. They can also assist you in narrowing down your topic or finding an aspect of the topic you may want to analyze further.
Remember, you do not need to read the entire book! Use as much of the book as you need.
Try using the table of contents or the index (located in the back of the book) to find chapters or pages that are relevant to your research.