Spotify pretty reliably finds me one or two interesting tracks in my discover weekly. That still leaves dozens of tracks I don't particularly care for (although I generally don't actively dislike them) but I still think it's a decent result.

I guess the obvious problem is that for books the equation is different. If you get recommended 20 books and after reading them you only ended up really liking 3 of them, then you'll feel like you've wasted a lot of time reading books you don't care for. Meanwhile if you listen to 20 audio tracks in the worst case scenario you'll have wasted an hour, and you can do that in the background while you do something else.