The poetry of William Butler Yeats presents unusual problems for the general reader. Yeats drew heavily upon mystical and theosophical systems of a more or less arcane nature. Moreover, he often referred to events in his own life and in the history of modem Ireland which require elucidition for the non-specialist. A Reader's Guide to William Butler Yeats not only provides the background needed for an understanding of the works but also reveals the structure of images and meanings of the various lyrics.
Excellent old fashioned critical discussion of Yeats' poems with a general introduction followed by one chapter on each of Yeats' collections. I was advised to read this while rereading the Collected: read a collection of poems, then read the relevant chapter in the Guide, then reread the collection he'd discussed. It is slow but well worth it even if you think you know Yeats' poems well. If good criticism has the ability to surprise and send you back to the poems you thought you knew, then this is good literary criticism.
This is the best starting point for any close-reading study of Yeats. It's imaginative, full of suggestions for future work, very interpretative. I enjoyed reading it. I would full-heartedly recommend it.