At an AASL conference in 2019, non-fiction author Melissa Stewart presented a different way of looking at nonfiction collections in school libraries. She first divides non-fiction into either expository (which describes, informs and explains) or narrative (tells a story or communicates an experience). Then she expands on expository by adding 3 other areas: traditional, browsable, and active. Her point is since studies have shown that elementary school students prefer expository non-fiction, this is a way to expand on the variety that is offered in school library collections. Check here for the full article.