So let me get this hypothetical and implausible situation straight, in my hands is the last copy known to man of a religion's holy texts, and the choices are, I burn it and live (longer than I was going to in the present situation), or I don't and die?
Well, if it's truly the last of its kind, then it means the religion's already died out, so there will most likely be no followers who will grief the loss of the book, I'll deeply regret it as I love history and archaeology and all that good stuff, but I'd probably burn it if it means saving my bacon, besides, what guarantee is there the text won't get damaged, destroyed or otherwise lost after my demise?
(Also, how would burning the book save my life?)