There are a number of major players providing audio services to libraries, 3M Cloud Library, Baker & Taylor, Hoopla and Overdrive. For the most part, these are the exact same companies that provide the libraries e-Book portfolio. In the US, 95% of all libraries have a digital collection and audio content is starting to play a more central role.
Audiobooks actually works fairly differently than e-Books do, on a business level. Many of the top distributors lean on 3rd parties for a full catalog of content. 3M and Baker and Taylor both get their audio editions from Findaway World, which is current market leader in production. Findaway has a catalog of over 50,000 titles and maintains production studios, narrators and crew in New York. Overdrive has their own internal solution, where they approach publishers directly and don’t do business with companies such as Audible or Findaway World.