Published in 1910 The Green Helmet and Poems is a fair collection of mid-period Yeats. There are a few of the frequently anthologized hits, "No Second Troy" and "The Fascination of What's Difficult," as well as plenty of more obscure and less successful poems. This slim volume does contain the brief and beautiful "A Drinking Song," which I think is Yeats most moving love poem and one you should read right now if you haven't before.