According to the Discworld reading order guide (v3.0), Reaper Man! is the second book in the DEATH thread of Discworld books.
Terry Pratchett – Reaper Man! (1991)
(Discworld #11, Discworld – DEATH Series #02) 🎧
‘Death has to happen. That’s what bein’ alive is all about. You’re alive, and then you’re dead. It can’t just stop happening.’
But it can. And it has. So what happens after death is now less of a philosophical question than a question of actual reality. On the Disc, as here, they need Death. If Death doesn’t come for you, then what are you supposed to do in the meantime? You can’t have the undead wandering about like lost souls. There’s no telling what might happen, particularly when they discover that life really is only for the living…
Note 1: 🎧 the unabridged audiobook for Reaper Man is narrated by Nigel Planer, 🎧 the abridged audiobook for Reaper Man is narrated by Tony Robinson.
❝”What is this thing, anyway?” said the Dean, inspecting the implement in his hands. “It’s called a shovel,” said the Senior Wrangler. “I’ve seen the gardeners use them. You stick the sharp end in the ground. Then it gets a bit technical.”❞
❝DROP THE SCYTHE, AND TURN AROUND SLOWLY.❞
❝Five exclamation marks, the sure sign of an insane mind.❞ *
❝WHAT CAN THE HARVEST HOPE FOR, IF NOT FOR THE CARE OF THE REAPER MAN?
— Death appeals to Azrael❞
In 1996 a short animated movie (pilot) ‘Welcome to the Discworld’ was made based on fragments of the Reaper Man plot.
 The Annotated Pratchett File v9.0 – Reaper Man
 Reaper Man (From Wikipedia, the free encyclopedia)