You wouldn't think about job security becoming a problem for Death, the Defeater of Empires, the Swallower of Oceans, etc., but of course the Discworld is itself a contradiction in terms. When your world is a flat plane of existence transported through space atop the four elephants astride the Great Turtle A'tuin's back, the impossible is surprisingly commonplace. In this bastion of animism and anthropomorphism, not only Death but the mysterious Auditors of Reality have been brought into existence via the mere consciousness running amuck throughout the world. These murkily-defined Auditors, who hate nothing so much as individualism, feel compelled to force Death into retirement for the simple reason that he had taken on something of a personality. If he actually has to die, Death is determined to at least live, and we soon find him working on Renata Flitworth's farm in the plains below the Ramtops under the assumed name of Bill Door. Whereas Death has been known to indulge his curiosity of living men and women from time to time, in this significant Discworld chronicle he slips into the ways of man without conscious effort, and to some extent Bill Door actually does live for a time on the Discworld.
Naturally, you don't just replace Death over night; it takes a while for the collective unconscious of all living things to formulate a New Death, and this period of temporary instability proves quite burdensome. One individual particularly unhappy about the current state of affairs is Windle Poons, the oldest of all the wizards in Unseen University. When Death doesn't show up to meet him at the appointed hour, Poons eventually has little choice but to go and reinhabit his old body once again. He's not the only undead person walking around in the days that follow. As if the walking dead weren't problematic enough, inanimate objects begin moving around of their own accord, little glass snow-globes begin turning up everywhere, shopping carts with minds of their own become a menace to society, and the wholly unnatural buildup of life force caused by the absence of a Grim Reaper opens a window on the Discworld for the insidious invasion of the most fearful of all creations.
Reaper Man, the eleventh book in the series, is truly one of the quintessential Discworld novels. We get to see plenty of Death and gain much more valuable insight into his outlook on life; his non-human humanity really shines through his skeletal essence on several occasions in these pages. The always-hilarious wizards of Unseen University are in the mix of things as they should be, and they are joined by a number of Pratchett's most singular characters. The remarkable Windle Poons, more alive than ever in his death, climbs out of the wheelchair of a very old, hard of hearing, mentally addled old wizard to become a very personable hero. For the first time we meet Mrs. Cake, the small medium seer who has a habit of answering questions just before they are asked, Mrs. Cake's daughter Ludmilla who happens to be a werewolf, the aforementioned Renata Flitworth, the Death of Rats, and the unforgettable members of the Fresh Start Club formed by zombie Reg Shoe. Those undead creatures who have decided to rally around Shoe's declaration that the dead aren't going to take discrimination lying down any longer include the reluctant vampire Arthur and his wife (Count and Countess Notfaroutoe), a banshee, an exceedingly shy bogeyman, and a wereman. Pratchett's wit and humor are in exceedingly good form throughout, making this one of the most enjoyable and inherently interesting of all Discworld novels.