Greg Pak 
Firefly: The Outlaw Ma Reynolds #1 [PDF ebook] 

After the shocking conclusion of Mal’s journey with Boss Moon, Mal hands himself into the Alliance…but it turns out its not him they want. The infamous Ma Reynolds is at the top of the Alliance’s Most Wanted, and if Mal doesn’t get to her first, the Alliance will! Kicking off a new year of Firefly, discover the secret history of Mal and his mother, and what that will mean for the rest of the ‘verse…and a new brewing war to end all wars.