Dark Souls III

[Brandon Storm]

They are nearly identical. The only differences being some page layouts/image layouts are changed to fit in either side book. Or rearranged since the sections are put together a bit differently.

From a quick glance, it looks like both of them have some small pieces of art that the other doesn't. But nothing important, I mean like one of them has a closeup on the detail of a handrailing, and the other has a little sketch of a tower that the other doesn't have.

All the important pieces are in both books. I would say you only need one. Of course the presentation in the bigger book is better, but if you have the smaller one, you're getting just as much as they have in the bigger one, I would say.