"I need it to fall asleep"

The last fill of the day is the one people defend hardest. The audiobook, the podcast, the radio on low. Without it the mind races and sleep won't come, and a book that takes it away is a book that costs you your nights.

Two things, and then a concession.

The first is what the last quiet stretch of the day is for. It's the only stretch, in a filled life, where the day could be sorted, and chapter 4 is about why that sorting feels unpleasant and matters. If every waking minute has been filled, the mind arrives at bedtime with a whole day unfiled, and when the head hits the pillow the filing starts, and it feels like racing, and the audiobook goes on to stop it. The racing isn't a fault of the night. It's the day's sorting, arriving in the only slot left, and being postponed one more time, to three in the morning, where the audiobook goes on again.

The second is that the audiobook isn't a chosen listen. You're not attending to it. You're using it to drown the drift, and you couldn't say, in the morning, what happened in the chapter. That's the hum, in the dark, and the hum has the cost chapter 6 described, which is attention paid in pieces to a thing you didn't choose, at the one point in the day when attention should be winding down.

Now the concession. Some people do sleep better with sound, and the book isn't going to argue with your nights. If the audiobook works, keep it. What I'd ask is two changes. Make it a chosen listen, a chapter you want to hear, with a timer, rather than a hum that runs until you're gone. And give the day a quiet stretch earlier, the walk home, the last ten minutes before bed with the light on and nothing playing, so that the sorting has a slot before the pillow and the pillow doesn't have to be it. Two earlier books in this series are about the evening and about three in the morning, and they're named in the notes. The short version is that a mind with somewhere to do its sorting sleeps better than one that's been fed input until the last second, and that the racing you're drowning is the sound of a day that never got a minute.