This is an English translation of the original in the Par Lui-meme series. Very occasionally the books in that series seem like glorified French cliff notes, but usually they are careful reflections on the authors in question, and often give insight into the work and thought of the author of the monograph.
That is certainly the case here. Boonefoy is a poet worth spending time with, and is a smart and very inclusive critic. So often English language critics and writers (John Ashbury and Patti Smith excluded) seem to think of Rimbaud only as a very smart and deeply troubled adolescent, but Bonnefoy takes him completely seriously and devotes serious attention to those incredible years when Rimbaud was 15 to 20 and produced all the work that we know. He draws the distinction between the visionary moments in the famous letter ("I is another" and "the complete derangement of all the senses"), the visions of "A Season in Hell," and wherever it was that Rimbaud got to in his "Illuminations." He makes a strong case for the influence of Christianity on Rimbaud, and the trauma of rejecting the religion. As just a taste of where Bonnefoy's thought takes us, here's the opening sentence of the last chapter: "Rimbaud stopped writing when the end of childhood, more compelling than any intellectual decision, deprived him of the hope that he could change life." And Bonnefoy has thought through the stages that led him to this conclusion. It is a book to return to.
And, of course, Bonnefoy returns us to Rimbaud's poems, even illuminating some of the obscure passages.
One little criticism: The French edition has a bunch of lovely photographs, and even reproductions of the holographs in Rimbaud's hand. Those actually help. I can't see why Harpers would have chosen, back in 1973, not to reproduce those, when they are done in the much more shoddily made object that is the French edition.
(And also it's worth noting that Rimbaud becomes another example of how difficult it would be to befriend genius)