Not actually how it works. Every author I know with a converted book or series sees increased book sales from those adaptations. Not less. a book makes the New York Times list with thousands of sales, but a low-rated TV adaptation still reaches at least 1 million people, many of them that never heard of the book(s) before.

People are absolutely reading books, especially across the globe. The global ebook market is booming in English-speaking countries that haven't reached saturation, yet, like India.