Dickinson never announces the end of summer. She lets it dawn on us the way the last chapters of a good book dawn on a reader: quietly, with a reluctance that creeps up before any decision is made. The opening simile sets this up. Summer has "the look" of a "Peruser of enchanting Book" who "Reluctantly but sure perceives / A gain upon the backward leaves." The syntax is bent, and the exact sense of "backward" is open to debate, but the feeling is clear. The reader senses that the pages already turned are gaining on those still to come. The pun on "leaves" does the real work. Pages and foliage are the same word, so the image of reading already contains the autumn trees it describes.
From there the poem dresses the landscape in clothes and trades. Autumn is only "inferred," as if detected like a clue, "By millinery of the cloud" (clouds fashioned like hats) or "deeper color in the shawl / That wraps the everlasting hill." The hill is "everlasting," yet it changes its wardrobe with the season. That tension between what lasts and what keeps changing is what the poem is really about. In the third stanza the workmen arrive. A "Dyer of a distant tree / Resumes his gaudy industry," and the word "resumes" makes the work seem routine, a craftsman returning to his bench after a break. "Gaudy" is a faintly teasing word, half admiring and half disapproving. Meanwhile the human response is double-edged. "The eye begins its avarice" casts looking as greed, a hoarding of colour before it is gone, while "A meditation chastens speech" suggests that the sight leaves us quieter and more serious.
Formally, the poem is made of four quatrains in lines of about eight syllables, with a steady, hymn-like beat. Dickinson keeps pulling against that regularity. The first stanza rhymes in tidy couplets (look/Book, perceives/leaves), which suits its comfortable picture of a reader and a book. Later the rhymes loosen. "Shawl" and "hill" only half-chime, "inferred" and "cloud" do not rhyme at all, and "tree" and "industry" rhyme only on a light final syllable. Punctuation nearly disappears, so clauses slide into one another, and the single dash at the end of the first stanza gives a small, breathless pause. Her capitalised nouns (Book, Dyer, All) make ordinary things feel like allegorical figures.
The last stanza is the hardest, and it should be read as a compressed argument rather than a clear statement. "Conclusion is the course of All" says that everything ends. "At most to be perennial" grants that the best anything can hope for is to return, as plants do each year. The final two lines, "And then elude stability / Recalls to immortality," seem to say that to escape fixed, final form is to be called back toward something deathless. The grammar allows more than one reading, and I would be wary of any reading that claims to settle it. Still, the direction is clear. A poem that began with a reader's small regret ends by asking whether endings are really endings, and whether the yearly cycle is a modest kind of immortality.
That movement is what makes the poem worth reading. Dickinson takes a familiar subject, the turn from summer to autumn, and refuses both sentimentality and plain description. She gives us a world run by milliners, dyers and readers, then lets that homely workshop open onto the biggest questions about time and permanence. The poem is also generous with its images. The book, the shawl, the hat and the dye-vat all make the same point from different angles: autumn is an act of dressing and revealing, and what we notice in it is our own awareness that things pass.