Literary theory - EAGLETON

Hi! I'm reading a chapter called: "What is literature"? the author is Eagleton.My question is: Why does the distinction between FACT and FICTION to define literature stand up to close scrutiny? Thanks for helping me.

If you are writing a book, you must decide whether it is fact or fiction, for the reader's sake. If someone wants to learn or research, they'll buy for facts or history. In between, a historical novel is still useful to both types of readers, but an author must establish a reputation of truth telling, generally, like James Michner and others.
Denis