I have several baby boomer friends that use audio books while they commute to and from work. They'd be lost without them. Some of these friends check out audio book CDs from the library, but many get their books online and download them to an MP3 Player or iPhone.
Now many libraries offer an option, through a company called Overdrive, for patrons to "check out" and download audio books from their public library's web site. I'm sure many boomers who have grown away from using libraries were unaware of this new service.