While there may be less demand for books, I am less sure of the corollary that there is less reading. I remember when Harry Potter was having its hey day, and the Amazon Kindle was first announced, there were stats showing that worldwide reading blipped up.
I suspect folks these days read faster, and read more words, than people past. Except it might be content like Hackernews, YouTube comments, X/Twitter and other doom scrollers, that make that up.