Three announced so far
Firefly: Big Damn Hero, by Nancy Holder (Oct. 2018)
Captain Malcolm Reynolds finds himself in a dangerous situation after being kidnapped by a bunch of embittered veteran Browncoats.
Firefly: The Magnificent Nine, by James Lovegrove (March 2019)
Jayne receives a distress call from his ex Temperance McCloud that leads the Serenity crew to danger on a desert moon.
Firefly: Generations, by Tim Lebbon (Oct. 2019)
The discovery of the location of one of the legendary Ark ships that brought humans from Earth to the ’Verse promises staggering salvage potential, but at what cost? River Tam thinks she might know …