A Natural History of the Senses, Diane Ackerman.
A Passionate Patience: Ten Filipino Poets on the Writing of their Poems, Ricardo M de Ungria.
Book of Luminous Things, Czeslaw Milosz.
Dreaming by the Book, Elaine Scarry.
Getting Real: an introduction to the practice of poetry, Gemino Abad.
How does a poem mean, John Ciardi.
How to read a poem and fall in love with poetry, Edward Hirsch.
Letters to a Young Poet, Rainer Maria Rilke.
The Demon and the Angel: Searching for the Source of Artistic Inspiration, Edward Hirsch.
Western Wind: an introduction to poetry, John Frederick Nims.
I feel like I'm missing a few more. Such as:
Seven Types of Ambiguity, William Empson.
Tradition and the Individual Talent, T.S. Eliot. (essay)