As a public figure that largely turned away from the public spotlight during his lifetime, Neil Armstrong has a relatively low number of biographies (he never wrote an autobiography). According to Nielsen BookScan, children's book Neil Armstrong: Young Flyer by Montrew Dunham is the bestselling title on Armstrong.
The bestselling adult title is First Man by James R. Hansen (Simon & Schuster), which was published in 2005 and has sold 53,000 copies at outlets tracked by BookScan. Following Armstrong's death on August 25, S&S will go back to print for 5,000 copies of First Man with a new foreword by Hansen, who has been interviewed about Armstrong by more than 30 news outlets, including NPR and PBS, in recent days. The edition with the new foreword will be available this fall--the book is still available in print and in e-book in the meantime.