You might like to read the Ellman biography of Yeats for more background.

Yeats's early poems were particularly influenced by sean-nos and the art poetry of pre-18c Ireland; later he moved into a lyricism of his own.

It's interesting to look at his poems in conjunction with his brother's (and his father's, indeed) paintings - his brother was much more a westerner, with his strong Sligo face, and much less a refined intellectual, though he was a fine, open-hearted man.