This is not unprecedented. When Milton wrote Paradise Lost , for example, he incorporated certain genre characteristics of previous verse epics into his own poem. The catalogue of opposing armies, for example, or the invocation of the muse. It's A Good Life. This is admirably simple.
Books are what the bookseller, or their catalogues, say they are.
A Study in Scarlet is Mystery. 1984 is literature, not science fiction. Maus is history. You find non-fiction books of historical research focussed around one person's life and times. They are researched and documented, with a whole apparatus of footnotes and documentation.