Kyle's book, "American Sniper," written with Scott McEwen and Jim DeFelice, was released last January. As of Tuesday morning, "American Sniper" was Amazon's No. 1 seller.
Rosenblum says no release date has been set for the new book.
Kyle left the Navy in 2009 after four tours of duty in Iraq, where he earned a reputation as one of the military's most lethal snipers.
Eddie Ray Routh has been charged in Kyle's killing Saturday.