Since her last Collected, 10 years ago, Anne Stevenson has written two volumes and several new poems. But she has also, it seems, spent a great deal of energy on the rearrangement of her oeuvre. It is now ordered in the manner of Wordsworth - by theme rather than by date. Thus all the poems on Cambridge are placed together and segue westwards into all the poems on Oxford, then west again into the Hay-on-Wye poems (this is a bookish and peripatetic poet), except when a Hay poem is also addressed to the poet's son, which means you will find it under "Seven Ages". It is an intricate, essentially musical arrangement: the recasting by this classically trained pianist of her life's work as a single symphony. It also seems certain to drive future scholars bananas as they flip through the index, trying to discover where the poems belong in real rather than musical time.

For Stevenson's sensibility has changed greatly over half a century, and it is frustrating to be prevented from charting this growth. Tucked into Section III (Haunted) is "Correspondences", surely Stevenson's masterpiece. This startlingly original verse-novel relates the story of a New England family over two centuries through a handful of their letters. Each letter is a tour de force, suggesting not only character and motivation, but the history behind the character, the history which becomes, in fact, the character. "Correspondences" was itself written in the teeth of a wind of political change, in the radicalising Cambridge, Massachusetts of 1970. In its pages, the symbolically named Mrs Chattle goes mad under the pressures that gave birth to the women's movement: "I'll try again. The marriage. / The baby. The house. The whole damn bore! / Because for me, what the hell else is there? / Mother, what, more? What more?"

Here is Sylvia Plath in her Bell Jar, or Anne Sexton, perhaps, deftly sent up at one of her weaker, more ululatory moments. Stevenson has distanced herself ever further from Plath and Sexton, whom she has characterised as "powerful word - witches ... who turned poetry into a particularly dangerous type of psychodrama". But in her early collections she also wrote free verse and entirely personal lyrics (some of the most affecting are about the death of her mother) and grounded her intellectual and metaphorical flights in autobiographical moments, as in her anthology piece "The Victory" or in this little erotic/ metaphysical gem, "Sous-entendu":

   Don't think
 

   that I don't know
   that as you talk to me
   the hand of your mind
   is inconspicuously
   taking off my stocking,
   moving in resourceful blindness
   up along my thigh.
 

   Don't think
   that I don't know
   that you know
   everything I say
   is a garment.
 

Latterly, though, Stevenson has shunned much contemporary poetry and largely eschewed the confessional or lyric "I". Her most recent poems remind of us of the consolations of Mozart, philosophise about writing, or are letters to dead poets. To complete the 18th-century effect, she has become fond of the couplet. At its best, this work is witty, spry and penetrating, but it sometimes seems that in turning away from the pressures of history and autobiography towards what she calls a more "classical" mode, Stevenson has also lost pressure from her language. Contrast these opening lines from the very recent "Prophylactic Sonnets" to those above: "Eyes fall in love before their users dare / Measure the turbulence behind their gaze, / So, without speech or touch, deep looks lay bare / The underside of smooth, well-mannered ways."

"Sous-entendu" is free verse but tight verse, knitted with consonances and driven by verbs. The sonnet, by comparison, thumps on its end-stopped rhymes. And it is hard to care about "users" of eyes.

"We hate," said Keats, "poetry that has a palpable design on us." Poems 1955-2005 rather too palpably intends to marmorealise Stevenson's literary reputation. She should not be so anxious. Posterity will just be readers, in the end, and they will have no trouble in remembering her "Correspondences" and very many of her striking, truthful, witty lyrics, with or without her grand designs.