If I remember correctly, in Object 56, it talks about how the B.N.T.G. distributed copies of the Cookbook, so I think that it would be possible to get a book published. I'm not sure about publishing a book, though, as in self-publishing. Although, considering the fact that Level 4 exists, I don't think printers are the most unusual sight, so if someone printed up a couple copies of something they wrote and started selling them, I think that'd count.
Now I'm wondering, what kind of books would people publish in the Backrooms? I think it'd be interesting to see a character who's just a humble author who goes around writing stories about the places he visits.
Also, what about CHILDREN'S books? Since animals aren't super common in places like Level 11, would there be children's books that use Entities as characters? That'd be an interesting tale to read.
Would there be books based on real stories of people in the Backrooms? Would people write about the Frontrooms? Could an Entity write a novel and publish it? What about biographies? Could someone in Sim Canon write a biography about the now-dead Overseers?
I should probably stop now. But, long story short, yes, getting a book published is definitely possible, and there's a lot of storytelling potential to tell about stories (see what I did there?) that are written by people in the Backrooms.