This unknown recommends Oblivion, a book of essays by Donald Justice (publ. in 1998). Should be a benchmark, lighthouse, guidebook.
In an essay on metrics, he debunks the notion that meters have some kind of organic basis (breathing, circadian rhythms, etc.). He offers a very persuasive (to me) interpretation of the paradoxical (subsidiary, understated) role they play, in the process of hammering together a memorious art work.
In a subtle essay on Baudelaire and "sincerity", written in 1957, he undermines the rationale for confessionalism - just a few years before that movement burst on the scene.
In an essay on Stevens' meters, he gives a sparkling mini-course on the "Imagist moment", followed by a discerning analysis of the pentameter background in Stevens, & what he did with it.
I'm loving this book.