There are other book vendors who've reached out to offer their affiliate programs, but I'm not sure any of them are worth it.

From the short time I was on Amazon, the lion's share of my affiliate revenue came from items other than books that were purchased using cookies that my app had set.

Without those non-book items, I would've made very, very little money (e.g., ~$5 instead of ~$300).

Books don't cost very much, but Persian rugs do! And there aren't many other booksellers out there who also sell Persian rugs...