The best known cast member of "Firefly" to have died since the series shuttered is Ron Glass, who played the mysterious preacher Shepherd Book. Book originally boards the ship as a passenger, but inexplicably remains on board, serving as an angel on the shoulder of Captain Malcolm Reynolds (Nathan Fillion), a man whose faith has been shattered by war. As the series progresses, however, it's made clear that Book was not always a religious man, and hints are dropped that he has a dark (and possibly classified) past. Both "Firefly" and the film "Serenity" end without that past being clearly defined, though Book's story did end up getting revealed in the comics.
As beloved as Glass is by "Firefly" fans, Book isn't the role for which he's most known. That honor belongs to his time on the Emmy-winning ABC sitcom "Barney Miller," in which he played Detective Ron Harris. Like Book, Harris stands apart from his colleagues; unlike Book, Harris is a bit full of himself, harboring dreams of a writing career and eventually publishing a memoir.
After "Firefly," Glass landed a number of recurring and one-off roles on shows like "Agents of S.H.I.E.L.D.," the legal drama "Shark," and a number of "CSI" series. He also enjoyed a good deal of voice work in animated series like "All Grown Up!" and the video game "Fable II."
Glass died of respiratory failure in November 2016. He was 71.
