Audible for Dogs is designed for anxious pets that don't like being left at home alone; Millan's Dog Psychology Center reports that audiobooks are much more effective in relaxing dogs and reducing their stress than music. The idea is pet owners will leave one of these audiobooks playing when they leave for work in the morning; whether in a crate or roaming the house, supposedly these audiobooks will calm dogs and help them feel less alone.
You can start with the free Cesar Millan's Guide to Audiobooks for Dogs, because apparently this whole program is complicated enough to require an entirely separate audio guide. The rest of the titles are handpicked by Millan and include a video introduction from the man himself detailing why exactly these books are good for dogs. Titles include Born a Crime by Trevor Noah, Pride and Prejudice by Jane Austen (these two definitely need an explanation because I'm not seeing the dog connection), The Art of Racing in the Rain by Garth Stein and A Dog's Purpose by W. Bruce Cameron.
This isn't a completely separate program; subscribers to Audible will be able to purchase these audiobooks, and anyone can access Millan's videos for free on the website. It's not clear what would prevent people from just buying regular, non-dog-selected audiobooks and playing them for Fido, but hey, I am not here to judge what you buy for your pet.