Titles are hard.
They are, above all other things, a type of signal to imply the impression of any given work.

For me it'd be best to go through titles and explain their "type" and their utility

Disco Elysium - za/um
It literally means "I learn Elysium". It's a simple, succinct title that subtly hints that this is the player's first view into the wider world of Elysium.

Guards! Guards! - Terry Pratchett
It plays off the central focus of the characters in the book being guards from the city's watch, implying from the get-go who the story's going to follow.

Sputnik Sweetheart - Haruki Murakami
The title speaks to the broader theme of the book, with it only being mentioned in passing rather infrequently in the book.

UNSONG - Scott Alexander
The title is a direct reference to the fictional organization within the text.

Homestuck, Undertale, Deltarune, Earthbound - Andrew Hussie et. al, Toby Fox, Shigesato Itoi
Relate to the literal central setting/concept of the story.
Homestuck, being stuck in a house
Undertale, a tale happening underground
Deltarune, spinning off of undertale and relating to a central object, the delta rune
Earthbound, literal reference to the characters (on earth) bound to fight giygas or giygas bound for earth.

The first three titles highlight the central "function" or theme of their respective stories, where the latter titles are referring to literal or not-as-literal scenario that the respective works explore.