The letters in question are in fact poems by Ted Hughes. The current printing does not appear to include an index. You might think that poetry volumes don’t need one. However, some poetry books include indexes of first lines as these may be better known that the titles of the poems. The reader is therefore helped by having the titles at the front and the first lines at the back. The lines are usually given as they stand in the text. Here’s a quick sample from the poems, might they make you want to read the poems more than the titles alone?

Lucas my friend, one
Our magazine was merely an overture
Stupid with confidence, in the playclothes
What were those caryatids bearing?
Where was it, in the Strand?