I used to distinguish between my fiction and nonfiction in terms of superiority or inferiority.
Peter MatthiessenFiction is harder for me than nonfiction - more gratifying, as a result, when it succeeds.
Rick BassI enjoy doing the research of nonfiction; that gives me some pleasure, being a detective again.
Joseph WambaughWhen writers stop believing in their own stories, readers tend to sense it.
Good Prose: The Art of NonfictionThe reader is someone with an attention span of about 30 seconds.
On Writing Well: The Classic Guide to Writing Nonfiction