In the sixties I dipped into this book for quotes to put in 'A' Level essays, but never read it fully.
Having finally got around to it it was probably just as well because much in the complexity of themes would have escaped me.
Yeats' life encompassed the turn of the nineteenth century and the drowning of the 'ceremony of innocence'. As a passionate Irishman, he was at the fulcrum of one of the vortices of this process. He was pivotally involved in the ongoing development of Irish nationalism and also in its cultural history, from Cuchulain (and before) to the Abbey Theatre. He brought to these concerns a rejection of conventional religion and a sustained and scientific as well as mystical approach to the occultism of Madame Blavatsky and others.
To Yeats all these belief systems, as well as his own development as a human being, were all intertwined, and even in a sense one and the same.
Ellman's biogrphy was first published in 1948, in a less sceptical age than ours, and he approached all Yeats' beliefs with no little understanding and appreciation. It is hard to imagine any academic now feeling able to give any kind of creedence to Madame Blavatsky: scientific dualism has given the world to the bankers, and now we cry, not even able to imagine how to get it back.
I have not read the much newer two volume biography by the historian Foster, but understand that Yeats' occultism is given short shrift.
Ellman to my mind in quite a short book by modern standards does a brilliant job of synthesizing themes, giving due weight to all and drawing out key points, especially, as another reviewer here or on Amazon.com has said, by drawing on eary unpublished versions of later published essays and poems.