This is the quintessential collection of the poetry of Yeats. It's dense and a bit difficult to get through, but the best part of the book are the detailed appendices and extensive explanatory notes. These both include long quotes from Yeats' personal writings, lectures and conversations, which help shed light on where the inspiration for his poetry came from. This is especially helpful with the Irish mythology that plays such a big role in his work. It's also delightful to discover that many of his poems came directly from dreams he had - several times he says he woke up and "took dictation" without anything extra added! The explanatory notes are so fascinating, I wish they had an index, so I can look specific stories up when I need to.