In a 2018 Pew survey, the plurality of respondents read print books only. About 3/4 of respondents read any book in the past year; only 1/4 read an e-book in the past year. The trend is flat-to-downwards. But audiobooks are on the rise.
Possible cause: Reading texts on computers is unpleasant.
Pew Research Center. (2019). 2019 survey on book reading formats. Retrieved from https://www.pewresearch.org/wp-content/uploads/2019/09/FT_19.09.25_BookReadingFormats_Methodology_Topline.pdf