Between the lines of "Last Letter"

Former British children's laureate Michael Rosen deconstructs the recently-published Ted Hughes poem "Last Letter," which recounts the days before Sylvia Path's death. What exactly should readers glean from this artifact, questions Rosen,  and can it be read for its poetic merit and not its relation to the famous poetic couple?

From the New Statesman:

“Last letter" (though it won't be the last word, to be sure) comes to us through years of briefing and fabling. Involuntarily, we may find ourselves playing out this poem as the Hughes and Plath of whichever biography we've read, or even as Daniel Craig and Gwyneth Paltrow. Is it Eng lit's celeb schlock, the awful detail pulped into goss and then extruded in end-of-year exams?

Rosen also recognizes the importance of repetition in the poem:

I suppose nothing concentrates the mind on questions of human agency more than being around suicide. Hughes finds explanations in mechanistics, Hardyesque fate and deterministic mythoi. I sense that he isn't completely convinced by this. From the first line onwards - "What happened that night? Your final night." - the poem is packed with repetitions of words. Within many of the lines and between pairs of lines, sounds repeat, too: "flame in a fuse", "Susan. Solitaire", "Jerked awake, in a jabbering alarm". On one level, this is the cohesion of poetry. On another, it feels like a special pleading: if I say something twice, you will be more convinced.