Premise: Mariner Books, a division of Houghton Mifflin Harcourt, was established in 1997 as a publisher of fiction, non-fiction, and poetry in paperback. Mariner is also the publisher of the Harvest imprint backlist, formerly published by Harcourt Brace/Harcourt Brace Jovanovich.
Hypothesis: More non-fiction than fiction titles get published by Mariner Books.