The short story "One for the Road" was featured in the Stephen King collection Night Shift and is a follow up to his novel 'Salem's Lot.
When Gerard (Eric Slodysko) is driving toward 'Salem's Lot, the exit sign he passes is spray painted with a red "eye" and the phrase "All things serve the beam." The eye is that of The Crimson King, the main antagonist of The Dark Tower series, the phrase is a popular saying within that universe. Coincidentally, 'Salem's Lot is one of the many interconnecting novels to The Dark Tower as Father Callaghan from 'Salem's Lot becomes a main character later on in The Dark Tower saga. This makes the story of "One for the Road" indirectly connected to those books as well.
The cover of the book "A House of Shadows" that Janey (Sandy Lawler) is reading, makes reference to other novels written by Ben Mears and also features reviews by authors from other Stephen King stories, such as Bill Denbrough (IT), Paul Sheldon (Misery) and Scott Landon (Lisey's Story).
On Gerard's GPS, the display shows that they are driving on Witcham Street towards Jackson Street. The intersections of Witcham and Jackson are where Georgie Denbrough meets Pennywise the Clown in IT.
There are several Easter eggs throughout the movie that connect "One for the Road" to other works by Stephen King, most notably 'Salem's Lot and The Dark Tower series of books. While driving in the car, Janey (Sandy Lawler) is reading a book by Benjamin Mears. Benjamin Mears, also known as Ben Mears, was the protagonist of King's novel 'Salem's Lot. Mears had returned to the Lot to write a book about the old Marsden house, though it was never finished. This was touched upon in the 1979 mini-series which One for the Road (2020) is a direct sequel to. In fact the opening lines that Ben Mears (David Soul) writes in the mini-series appear in the book that Janey is reading. It is supposed that Ben Mears finished the novel Janey is reading after the events of both the 'Salem's Lot book and mini-series.