I've owned this selected volume for probably a decade and a half and while I've leafed through it many times, nothing could prepare me for reading it cover to cover. I had no idea, first of all, how damned difficult Montale could be, especially in his middle period (the late 30s and early 40s). In particular, the poems called "Motetti" from Le Occasioni are as dense as any koan. The work selected from Ossi di Seppia (first book) and La Bufera e altro (later in his career) is certainly less opaque, but only in a relative sense. A difficult English poet like Eliot or Geoffrey Hill can often be tamed a little by simply looking up the allusions, but this is not so easily done in a foreign language, and besides, according to the preface, Montale's allusions tend to be more along the lines of "a Dantesque word" rather than anything more substantial (this is just one of many reasons why I question the constantly-invoked Eliot comparisons).
Nevertheless, these poems are astonishing. Every image, however, inaccessible it might be, is breathtaking in its originality and power. The voice is one of authority, profundity, and sorrow—often intensely personal, rarely "public" as comparable English poets tend to be. It's been noted before that Montale tends to begin in medias res, which is one thing in an epic but quite another in lyric poetry; many of the events and images are presumed to be entirely private to Montale and his circle, although we do know the identity of some of the absent women in the poems, such as Irma Brandeis, who gets the Catullan (or Petrarchan) alias "Clizia." But Montale rejected any association with "hermeticism," and it's true that with a few exceptions, the intensely personal image tends to broaden into a reflection that works on a broader level. The difficulty never repels; indeed, it calls one back to go over and over the lines. These finely-wrought poems (Montale was by no means prolific, and I presume this reflects his craftsmanship and tendency to revise) are the sort that will keep on giving.
Just a brief note—especially since Montale picked up the Nobel, much of his work has gone through multiple translations. This volume relies on several, and in two occasions, offers two separate translations of the same poem. The Italian is provided on the left for reference, and while my Italian swiftly drowns in Montale's deep waters, I know enough to tell, for example, that Robert Lowell's translation of "Notizie dell'Amiata" is so loose as to be nearly a recomposition (beautiful in its own right). So you get about as wide a range as you can get in English—literal, loose, and in between. A few translators have an annoying tic of dropping into a kind of Elizabethan English, with verb endings like -est and the pronoun "thou." I can only presume this is meant to address a use of a T-V distinction that English has lost, or perhaps a use of archaism on Montale's part, but the effect is strange and extremely jarring in English, and some kind of explanatory note would be very helpful in those places. Otherwise, the experience is of reading fine English poetry throughout.