Not strictly speaking a Signed Poetry Book but we don't let small details get in the way. I bought a copy of the 1970 collection, Lucidities, with a signed letter 'inlaid'. That letter turns out to be a routine but very gracious reply to a fan letter. All poets will know that fanmail arrives by the vanload every day. First class postage in 1974 was three and a half new pence.
It is also a quite charming book, though not immediately obvious in retrospect how Elizabeth had really developed 'a new style' as she explains in the enclosed Poetry Book Society leaflet but it must have seemed like a departure for her at the time.
I look forward very much to the biography in September when we can intrude further into the life of this modest, if not quite unassuming poet, who already seems like somebody likeable but almost quaint from a bygone age, much to her credit.