I need help with a reading challenge – 2 books in a shared universe that aren’t in a series

This one has me stuck yall im about half way though the challenge and I can’t think of a pair of books for this one. I know SJM technically has a shared universe but I’m not ready to jump back into that yet. I prefer thriller / horror books. Thanks in advance for the help.

I have pasted the prompt below 👇

1. A crossover (set in a shared universe)
   Prompts 28 and 29 are connected. Your book choice for 28 will influence prompt 29.

A shared universe is when two or more standalone stories take place in the same world setting with the same continuity. This means that one story has the potential to influence events in another story, or that characters from one standalone novel may bump into characters from another standalone novel. (Note: This is different than books in the same series, although books from separate series may share a universe.)

For this prompt, you may pick a book with a character crossover or character cameo (For example: the main character in book one enters a coffee shop and bumps into the main character from the author's previous novel). You might choose a location crossover (For example: the main character in one book visits or references a bar owned by a character in another book), or the book may reference events or information from another book. Books in a shared universe may or may not share characters.