As usual, when I don't know what to say about a genre, I'll direct you to Wikipedia. I will say that I usually have no interest in documentaries, but from time to time I may watch one, if the subject matter is of particular interest to me. For quite awhile I thought I wouldn't bother even having a documentary category in my movie reviews section, but... eh, I guess I might as well start one, even if it'll only have a few entries.

See also documentary web films, nonfiction books, informational shows, and the "documentary/reality" subheading in special presentations.