One of the most famous poets of the 20th century, William Butler Yeats was so popular and renowned during his time that he was the leader of what came to be known as the Irish Literary Revival, on the strength of his short stories and vivid poetry. Eventually it would lead to his winning a Nobel Prize in 1923.
Before Yeats won awards, his interest in spirituality and folklore drove him to write at length about Irish mythology and the occult before the turn of the 20th century. In many ways, it was Yeats who popularised the characters of Celtic mythology and medieval Irish folklore for contemporaneous audiences.
"Ideas of Good and Evil" is a collection of essays about art written during the late 19th and early 20th centuries. His thoughts on symbolism versus allegory, art as "the theatre of commerce" versus art as a "great Passion" are marvellous. This book is a real treasure and one to add to the collection.