Nonfiction comprehension can be approached in several ways. Generally, the best way to start is to read the text closely and attentively. Make sure to take notes as you read - this not only helps with understanding, but also facilitates retention. You should also be sure to pay close attention to headings and subheadings, as they often give insight into the overall structure and flow of the text.
While reading, you should use a variety of cognitive strategies to help with understanding. For example, pause frequently to reflect on the text and consider the implications of what you've just read. Use your past knowledge to draw connections between what the text is saying and other facts and ideas you already know. Take the time to look up and explore any unfamiliar terms or concepts.
Once you feel that you have a good understanding of the material, it is time to start testing your comprehension. Ask yourself questions about the text, and look to the material you highlighted and summarized to answer them. Reflection questions could be anything from “What is the main point of this text?” to “How do the author's arguments support the conclusion they drew?”
With enough practice, you’ll be a nonfiction comprehension pro in no time!