Fire certainly comes into play throughout the novel. The Sisters of Battle believe that the only good witch/mutant/heretic/traitor is one who's not only dead, but burnt to a crisp. Meanwhile, their psyker enemies often retaliate with "witch fire." So in just about every combat scene there's flames, screaming, smoke and burnt-flesh odors.
I found Faith & Fire to be a predictable, but entertaining story and give it a 3-star rating. The finale has an element of Deus Ex Machina to it. However, this can be justified, since the story revolves around the characters' religious zealotry for the God-Emperor.
Readers generally liked Faith & Fire, which has a 3.5-star rating on both Amazon.com and Goodreads. Warhammer 40K fans either loved it, or hated it. The fans who disliked the book thought the characters were wooden, flat, unremarkable and even unlikable, along with sounding more like men, than women.
I didn't pay attention to these valid observations, because the characters are members of Imperium's Church Militant. Their lives revolve around prayers, singing hymns, and incinerating the enemies of the God-Emperor. This doesn't leave much room for deep character development, or more feminine pursuits, beyond religious fervor.
Faith & Fire does follow the standard story lines of the Warhammer 40K 'verse--
--The heroes demonstrate insight and initiative.
--Which in turn, causes them to run-afoul of their dogmatic superiors.
--The agency the heroes are members of have a hidden agenda.
--Which in turn, runs afoul of one or more other agencies operating on their own agendas.
--There's a conspiracy afoot to take over a planet/star system/quadrant/the entire Imperium.
Despite these standard tropes, I still liked Faith & Fire enough to start reading the sequel, Hammer & Anvil, right off the bat.
I'm a retired USAF TACP (Tactical Air Control Party) member, now working for Washington State Emergency Management. In addition to being an Emergency Operations Specialist at my day/night/weekend job, I'm a Foreign Affairs Specialist, gamer and writer.
I maintain three blogs as an on-line platform. "Stern Rake Studio," my central site, explores a variety of topics on gaming, pop-culture and writing. "Station WTFO" is where I post comments and discussions on the national and international issues that concern us. Finally, "The Redshift Chronicles," is a spin-off of "Stern Rake Studio." This site focuses on sci-fi gaming and is home to my long-form webcomic "Breakout from Bongolaan."