Hello Kelly,
I don't know if the book is still in print. You might check with the Duvall Society in Maryland (Prince George's County I think) or the Prince George's County Genealogical Society there. If you Google for it or do a search on Amazon, you might also be able to find copies new or used. I think the official name of the Duvall Society is "The Society for Descendants of Mareen Duvall". They were helpful to me in the past, and I believe it is them who publish and re-publish the book from time to time. Good luck! Sharon