The first one looks like the books are covered into a plastic foil.
The second shows some sharp edges on the bottom book.
The third one looks a littlebit like a leather book cover, with a pattern stamped onto it.
The Pages (Paper) are looking alright, but on the top book it looks a bit off on the top border. Maybe built a texture where you have more thin lines in the paper texture, because right now it could be also pressed wood plates. (especially the book in the middle)
Even if it is not the main focus, i want to mention that you could built the gab on the wood floor, to make it a bit more realistic. as i can see it’s a normal map (or bump map) that controls the shadows for the gap. But when you take a look at the transition of the wood floor and the book, you will see that it destroys the realism, because there is no real gap on the mesh.