Discworld 11: Reaper Man by Terry Pratchett
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They say there are only two things you can count on ...
But that was before DEATH started pondering the existential. Of course, the last thing anyone needs is a squeamish Grim Reaper and soon his Discworld bosses have sent him off with best wishes and a well-earned gold watch. Now DEATH is having the time of his life, finding greener pastures where he can put his scythe to a whole new use.
But like every cutback in an important public service, DEATH's demise soon leads to chaos and unrest -- literally, for those whose time was supposed to be up, like Windle Poons. The oldest geezer in the entire faculty of Unseen University -- home of magic, wizardry, and big dinners -- Windle was looking forward to a wonderful afterlife, not this boring been-there-done-that routine. To get the fresh start he deserves, Windle and the rest of Ankh-Morpork's undead and underemployed set off to find DEATH and save the world for the living (and everybody else, of course).