Not just eBooks: the growing popularity of audiobooks has presumably had an effect on traditional book sales too.
Audiobook sales continue to grow strongly every year, where as ebooks have been flat or declining in recent years.
that's more about a desire not to read, with the (IMO flawed) strategy of multitasking, vs. format. The % of people who have read a book in the past year is abysmal and continues to decline.
I see audiobooks as crazy expensive and I don't like how they are locked down. If I paid $20-30 for a Martin Prechtel audio book and get an MP3 or something I could use any way I like it would be one thing but to be locked into Apple or Amazon it is just something I do when I am on the free trial... And Prechtel is one of very few authors I'd prefer it for because his work is so oral.