From what I understand, Tales From the Gas Station started out as a series of short stories posted online (on Reddit I think?). The episodic nature of the originals has been smoothed over by the author to make this more cohesive but all the original elements are here.
This book is the story of Jack who works the night shift at a gas station / convenience store owned by a mysterious older couple and located out in the boonies. The location is never really specified but it's somewhere in the southeastern U.S. Jack also has some kind of permanent insomnia so he never sleeps and, well, sometimes works multiple shifts or even a full 24 hours. The gas station itself is the locus of a lot of bizarre supernatural events as if it were, I dunno, cursed/haunted/built atop an interdimensional rift or old Indian graveyard.
Jack is a young 20-something guy who is patiently waiting to die (his condition is fatal, he explains) and who lacks any particular ambitions hence he works at this gas station. One night an unusually strange person walks into his store (I say unusually strange since he has a "usual" set of strange characters and aggressive raccoons that he deals with on a regular basis) and things start going downhill from there. From the earliest pages of the book, strange and bizzare events start occuring and Jack faces them down with, initially, a refusal to accept that it can't be explained away, and also a refusal to "get involved" so he's really a rather passive observer at first. But the universe won't let him stay that way, and he ends up getting involved in one ridiculous irrational situation after another and it becomes hard to keep track of everything going on. So to keep himself stable (and upon suggestion from a friendly sort) he starts to keep a journal of everything that is happening to him. That journal is ... quelle surprise ;-) ... these books.
There are numerous secondary and tertiary characters, some are just throw-away bits, others become more fleshed out as the story progresses. There's plenty of original takes on some classic horror tropes, a handful of entirely original concepts, and lots of fun. I'm sure other reviewers have already spilled the beans on various situations and characters, so I'm going forego any detailed descriptions and simply say this is a very fun read. If you like horror comedy then you should find this quite entertaining. Violence is moderate-to-minimal, there's some foul language, no sex to speak of, so it's mostly a PG-13 kind of book, soft R at the worst.