Look, I can't believe we're even seriously having this conversation. Printed book sales are declining every year. Not to mention that 1 in 20 books sold last year in the UK were 50 Shades of Grey. Not exactly a great sign?
And you don't think that has anything to do with the emergence of tablets, e-readers, or people reading books on their telephones?
The truth is, "average adults" read more now than they have at any time in the last 100 years. But "reading" encompasses a broad range of things--everything to blogs to online news articles to posts on message boards. And, these days, fiction has taken a back seat to non-fiction material, but that's been true for most of the life of the printed page. Fiction didn't really start to become popular until the mid to late 19th century.
And even so, people now read more fiction on average than they did in the 80s and 90s.