Well, it might also suggest that the wife, while drunk, is so into a story that she doesn't want it to end. It could be a story that has some sort of emotional connection for her, like a love story that reminds her of her own relationship, and the alcohol has made her more fixated on it, so she just can't get enough of it.
It's not a common expression at all. However, we can infer that intoxication can sometimes lead to an intensified interest in something. In this case, the wife's drunken state has made her really into the story. It shows how alcohol can influence our perception and engagement with different elements in our environment.
Well, it could be that the art style is amazing and the plot has a lot of twists and turns that keep you hooked. Also, the development of the characters might be really well done, making you care about them and want to keep reading.
Perhaps the world-building in the novel is so rich and immersive that you just can't get enough. Or it could be that the emotional depth of the story and the growth of the characters resonate strongly with you.
It could be that Levi is injured. In many fanfiction scenarios, the character might have sustained some sort of injury that affects his ability to get on the horse. For example, a leg injury would make it physically challenging to mount the horse.
I think it could be that the art style is amazing and the storylines are full of surprises and emotions. Plus, the characters are very relatable and easy to root for.
A 'sakura i cant be with you fanfic' might also play with the idea of timing. Maybe they meet at the wrong time in their lives. Sakura could be on a different life path, focused on achieving certain goals, and the relationship would be a distraction. Or it could be a story about growing apart over time, where they start close but gradually their lives lead them in different directions, making it impossible to be together.