Reaper Man (Discworld, #11; Death, #2)

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).

The Discworld novels can be read in any order, but Reaper Man is the second book in the Death series.