Even if I didn't work for ALA Publishing, I'd still recommend the new issue of Library Technology Reports. When it's Tom Peters writing, the topic almost doesn't matter, but he's such an expert on the topic of audio ebooks that this can be considered the current primer.

Digital Audiobook Services through Libraries

"Author Tom Peters explains that his issue of Library Technology Reports, 'examines in some depth digital audiobook services that can be purchased or leased. It also looks briefly at a few free online digital audiobook sources.'

According to the author, who is a librarian and an avid user of audiobooks, 'The purpose of this report is not to convince librarians to implement a digital audiobook service, but to help librarians make an informed decision.' "

Disclaimer: Tom is also a friend of mine. :-)