When viewing a list of book panes, often users want to to be able to toggle to a cover view, to have a better, more efficient, browsing experience.
So excited for this feature! I find it super helpful when having a look at everything I've read in a year and being able to have it all on one screen :)
That's certainly part of it! There's also aesthetics at play! And what people want to screenshot! :-D
This is my exact reason! I make monthly wrap-ups that I post on Instagram, Facebook, and LinkedIn - currently I am going back to Goodreads to screenshot from my reading challenge there.
This feels like part of a more general feature for making pages more or less dense. For example, more dense might reduce the font size and white space. It's an interesting UX question whether you want a single scale (less dense <-> more dense) or you want separate controls for cover on/off, font size, white space, amount of data displayed per item ...