Yes, I have annotated and closely read a nonfiction text, and it helped me in the following ways:
I was able to locate important information in the text quickly.
I could identify the central idea of the text.
I understood the development of the ideas and arguments in the text.
I highlighted and looked up new vocabulary and concepts in the text.
or
No, I’ve never annotated a nonfiction text or tried to do a close reading of it. Whenever I've read nonfiction, I had the following problems:
I had a hard time understanding what the work was about.
I wasn’t able to locate the central idea of the text.
I had an incomplete understanding of how the ideas and arguments were developed.
I didn’t mark off any words and concepts I didn’t understand, so I never looked them up.