The Songs of Eretz MOOC ModPo Poem of the Day for September 9, 2014 is "Tell all the truth but tell it slant--" by Emily Dickinson. A link to the poem may be found here: http://www.poetryfoundation.org/poem/247292. Dickinson's poetry has been examined many times in the Poetry Review. A brief biography and references may be found here: http://eretzsongs.blogspot.com/2013/12/review-of-its-all-i-have-to-bring-today.html.
"Tell all the truth but tell it slant--" is a nearly traditional rhyming ballad in strict iambic tetrameter with a deliberately dropped foot every even line. The use of capital letters, a bit archaic even in Dickinson's day, is presumably for emphasis. The first and last lines end with Dickinson's signature, enigmatic dash.
The poem is a bit of advice from the poet to the reader about how to go about telling the truth. Dickinson suggests to "tell it slant--" which may mean to come at the truth tangentially, gently, lest its truthiness cause panic, as a panicky mind will not be receptive to learning the truth. In the second line, Dickinson echoes the first, suggesting a "Circuit" or circuitous route to the truth. The raw truth is too much like "Lightning." The "dazzle" of the truth is "blind[ing]." Dickinson suggests approaching the truth in the way that an adult might explain what lightning is to a child. One would not want to go straight to the scientific truth here, as that might frighten and confuse. Instead, one might tell the child a story or recount a myth about lightning at first, and then "gradually" get to telling "all the truth."
From a meta-poetic perspective, the poem is a recipe for writing a good poem (such as this one). More than prose, or even visual art, poetry involves, among other things: metaphor, form, multiple meanings, context, and texture; the white spaces in a poem may have more meaning in them than the words. Some poetry enthusiasts, such as Dickinson, would argue that poetry is the best or even only means of conveying "all the truth."