 Ron Glass as <unk> Book — a Shepherd ( equivalent to a pastor ) . Although presented as a devout Christian , Book has profound , unexplained knowledge about criminal activities , police corruption , and military strategy , tactics , and weapons . In " Safe " , he was shown to have sufficient status in the Alliance to receive emergency medical treatment from an Alliance ship , with no questions asked . He is also proficient in hand @-@ to @-@ hand combat and the use of firearms . While objecting to violence most of the time , on a rescue mission he joins the fight , stating that while the Bible is quite specific about killing , it is " somewhat fuzzier on the subject of kneecaps " . Book is a moral guide for Mal and the rest of the crew , a voice of reason , conscience and spirituality . At the same time , he seems to get along well with the amoral mercenary Jayne , with the two spotting each other while working out using a bench press . His hidden backstory would have been gradually revealed , had the series continued , but was instead explored in the 2010 comic book The Shepherd 's Tale . 
