A Mighty Fortress

A Mighty Fortress is a science fiction novel by American writer David Weber. The fourth book in the Safehold series, it was published by Tor Books on April 13, 2010. It debuted at #9 on the New York Times Bestseller List for hardcover fiction, following in the steps of previous titles in the series which also debuted on the list. The book dropped to #24 in the second week, then to #29 in week three before dropping off the list, for a total of three weeks on the list.