This book is old enough that it is available for FREE.  Written by Willian Hope Hodgson, you can read it here

https://www.gutenberg.org/ebooks/10002

or listen to a pretty decent reading here:

https://www.youtube.com/watch?v=KcG1F39GBA8

This came up in a conversation with my cousin recently, because this is one of those books that I felt was highly ahead of its time and I'm constantly recommending people to read.  But there's always this one hitch.

It is, factually, the ONLY book that ever gave me nightmares.  The pig beast from the book is one of the few to rate a plate in Barlowe's Guide.

The problem being, when I mention this, peole that know me say... "There exists a book that could give YOU NIGHTMARES?!  Nope nope nope.  I mean, your JOKES give me nightmares, I don't even want to know what gives YOU nightmares."

And that's unfortunate, because this was a genre-defining book.  This was H.P. Lovecraft, before Lovecraft knew what a Cthulhu was.  This was a story about a universe that didn't know of or care about you.