Oh, erm, this wasn't what we expected... Seems the Pratchat book summoning circle has chosen ERIC for our episode… twitter.com/i/web/status/9…—
Pratchat Podcast (@PratchatPodcast) April 04, 2018
According to LSpace’s Discworld reading order guide (v2.21), Eric is the fourth book in the Rincewind thread of Discworld books.
Terry Pratchett –
Faust Eric (1990)
( Discworld #09, Rincewind #04 ) 🎧
Eric is the Discworld’s only demonology hacker. The trouble is, he’s not very good at it. All he wants is the usual three wishes: to be immortal, rule the world and have the most beautiful woman fall madly in love with him. The usual stuff. But what he gets is Rincewind, and Rincewind’s Luggage into the bargain. Terry Pratchett’s hilarious take on the Faust legend stars many of the Discworld’s’most popular characters in an outrageous adventure that will leave Eric wishing once more – this time, quite fervently, that he’d never been born .
Note 1: 🎧 The audiobook for Eric is narrated by Stephen Briggs
The subtitle to Eric (‘Faust’, crossed out) already indicates what story is being parodied in this novella: that of the German alchemist and demonologist Johannes (or Georg) Faust who sold his soul to the devil. 
❝No enemies had ever taken Ankh-Morpork. Well technically they had, quite often; the city welcomed free-spending barbarian invaders, but somehow the puzzled raiders found, after a few days, that they didn’t own their horses any more, and within a couple of months they were just another minority group with its own graffiti and food shops.❞
Wish 1: To be Ruler of the World – The local people come forward to pay tribute to Eric and declare him Ruler of the World. Da Quirm tells Rincewind about the terrible fate the Tezumen have planned for the Ruler of the World, on whom they blame all life’s misfortunes.
❝As they said, you always knew where you stood with Quezovercoatl. It was generally with a lot of people on top of a great stepped pyramid with someone in an elegant feathered headdress chipping an exquisite obsidian knife for your very own personal use.❞
Wish 2: To Meet the Most Beautiful Woman in All History – Both Eric and Lavaeolus are disappointed to find that it has been a long siege, and Elenor is now a plump mother of several children, with the beginnings of a moustache, and that serious artistic licence had been taken in her description.
❝“But I read where she was the most beautiful—”
“Ah, well,” said the sergeant. “If you’re going to go around reading—”
“The thing is,” said Rincewind quickly, “it’s what they call dramatic necessity. No one’s going to be interested in a war fought over a, a quite pleasant lady, moderately attractive in a good light. Are they?” ❞
Wish 3: To Live Forever. – Rincewind and Eric are left on the newly formed world, with the realization that “to live forever” means to live for all time, from start to finish
❝“That’s what I’ve been saying,” said Eric, with strained patience. Rincewind took another bite of the sandwich. He’d looked death in the face many times, or more precisely Death had looked him in the back of his rapidly retreating head many times, and suddenly the prospect of living forever didn’t appeal. There were of course great questions he might learn the answer to, such as how life evolved and all the rest of it, but” ❞
❝Multiple exclamation marks,’ he went on, shaking his head, ‘are a sure sign of a diseased mind.❞
❝The gods of the Disc have never bothered much about judging the souls of the dead, and so people only go to hell if that’s where they believe, in their deepest heart, that they deserve to go. Which they won’t do if they don’t know about it. This explains why it is so important to shoot missionaries on sight.❞
❝Any wizard bright enough to survive for five minutes was also bright enough to realize that if there was any power in demonology, then it lay with the demons. Using it for your own purposes would be like trying to beat mice to death with a rattlesnake.❞