Audible vs Spotify's audiobooks feature

Hello! I've been getting into audiovooks recently, and have mainly used Spotify to listen to them. However, I hate the fact that despite Spotify has all these books for free, they have heavily limited hours. And buying an addition to your premium sub only gives 10 more hours to 15hrs per month.

Would Audible be a worthy replacement? From what I understand you do have to purchase books to listen to them on it, but also get a credit for a book of your choosing every month. But does Aduible have unlimited hours? And offline support? I apologize if the ladder are stupid questions, looking at what its subscription plans are doesnt explain them, that or I just can't read