In these modern times of ours, the word literally has taken on a new meaning, which is "not literally but with emphasis." This seems like the most likely explanation.

Even if that's the intended meaning of literally, it is still a reckless exaggeration. I'm pretty sure that Stephenson's endings are no more abrupt than some of Shakespeare's (check out Hamlet and Macbeth) or some of Frank Herbert's (see Dune and Children of Dune), and I never hear anyone go out of their way to describe either of them as being unable to write endings.

I interpret the sense of "literally" here in the opposite way, i.e. without it the sentence may be taken to mean that the books metaphorically stop mid-sentence, but with it, they're saying that it's non-metaphorical and they really do. It would be bizarre wording otherwise.

These modern times that literally began in 1769. Oxford English Dictionary, “literally (adv.), sense I.1.c,” June 2025, https://doi.org/10.1093/OED/9189024563.

The use of the word "literally" to be used as emphasis started in the 1700s, and people have been complaining about it since at least 1909

https://en.wikipedia.org/wiki/Literally#As_an_intensifier

“Literally” is commonly used as emphasis, but not as hyperbole. So it’s still a misleading misrepresentation just the same.

literally

Hard to believe this when it's such a cut and dry claim about text. What does exaggeration even imply in that context?