In one of my college classes, we've begun a discussion of 'genre'. What is genre? What kinds of genre exist among books? Not just a theme like 'sci-fi' or whatever, but form as well, such as 'biography' or 'non-fiction' or 'poetry'. Opinions?

I disagree with your idea of theme. To me, a theme is something like "rejection of society" which can fit into any genre, which I would say is something like "Sci Fi" or "Fantasy".

I kind of agree with Carzeebear. 'Biography' is more like a type of book. 'Fiction' or 'non-fiction' is a classification and 'thriller', 'mystery' and so on is a genre.

Agreed with Carzee and Pyro.

what describe are classifications-fiction/non-fiction-, theme is the lesson, and genre is the type- mystery/romance/comedic.