The Silmarillion
Don't get me wrong - I love Tolkien. I am by no means a Tolkien scholar, though, or even an extreme nerd (like I can't tell you all the chapter titles in The Hobbit). I am a casual consumer of Tolkien, but have been so for almost 50 years at this point, so it's baked into my bones.
When I have insomnia, which is way more often than I would like, my go-to audiobook is "The Silmarillion", read by Andy Serkis.
When I'm trying to fall asleep, because of my auditory processing issues, every third words or so seems like nonsense to my brain, because it is a Tolkienesque word (and I can't see it on a page to make sense of it, because I'm not following along, because I'm trying to fall asleep).
Andy Serkis does a fantastic job reading Tolkien. I loved his rendition of "The Hobbit." The only issue I have is when he uses a "dragon voice" and I don't know that he's going to do it, because his dragon and goblin voices (and heck, Gollum's voice, even) are very scary and not sleep-inducing!
Just a side note, there are a lot of female characters in this tome. Ahem.
Last night I wrote a paragraph of what The Silmarillion really sounds like to me when I'm listening to it at night when I have insomnia:
"And then, garbledweirdnameguy went up the mountain nonsenseword to fight Pgibbedyflubbit, the elven king, and thus pinned him to a tree, on which he died. Nonsensename's daughter fell down into a darkness of grief which was akin to death. By his quest for the king's daughter, he knew this blahdedyblah was the true Psnirkelmuffin, and he was full of regret. Smarkmarken took up the call to Nonsenseword once the fell winter had ended, and came at last to Pookymirfy, where he was lauded in the halls of Snorkmastron in hopes that Randomwoman's daughter, who was vain and full of grief, would reveal the coming of the Mablapmore without waking the dragon, terrible Spibbeldysmish, who slay horses for sport, and ruled the mountain of Dorynorypory for years, darkening the valleys of Porbolimos with his stench."