THE library created sides of the library for classification: as fiction and non-fiction, placing poetry in the non-fiction (based on presenting reality as it is happens or is happening: inc. memoir, biography, and philosophy), done not to be complex in design by not making poetry a third separate section.
But poetry can at times be classified as both fiction and non-fiction: such as by telling a story in long verse like The Odyssey by Homer or Beowulf, or a novel being both poetry and fiction, like Ulysses by James Joyce or The Waves by Virginia Woolf, or mainly fiction in structure with dialogue and action, and also containing lyrical passages like Song of Solomon by Toni Morrison. Short narrative poems like ones by Robert Frost may tell a fictional story as a poem. A lyric poem can express a reaction or view without fictional elements like character or situation. But the place of knowing is in reading as many poems as you desire.
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A poem may transcend the poet and subject, and yet it is true: a moment may pass but in a poem it is always happening.—Jade
Blush of Dawn 