A research paper, a newspaper article, a short story are the expository writing.
A diary, a poem, an essay on friendship are the other types of writing.
Expository writing
Expository writing is used to communicate facts (as opposed to creative writing, such as fiction). It is the language of learning and comprehending our surroundings. You've probably come across examples of expository writing if you've ever read an encyclopaedia entry, a how-to article on a website, or a chapter in a textbook.
Scientific reports, academic essays, and magazine articles are some of the most common types of expository writing. An expository writer cannot presume that potential readers already know or understand the content they give.
The direct characterization is "keen black eyes." In this context, it makes the man seem curious, cunning and/or perhaps suspicious, as it implies that he is thinking deeply about the situation and the "things."
