Be forewarned, Milford is sexist and heterosexist to an educated modern reader and paternalistic towards her subjects. Furthermore, she seems to be listing what Millay does instead of telling/narrating it. 
 Biography is the art of making data into a story so the reader can feel they knew the person whose life is told; Milford does not accomplish this. Unsurprising when she sometimes lists such an inspiring documents as lists of repairs to be made to Millay's home. That said, Millay herself is such an interesting person and her poems (quoted abundantly) are sometimes so good, there is something to be taken from this book. Still, wouldn't recommend it. 
 I was also bothered by the unexplained shift from 'Vincent' to 'Edna' to refer to the subject.