Overall, you've done a great job and produced a nice image.
Couple of things you could pay some further attention to:
• I agree with alejande: you need to do something about the floor texture. It does look like the normal or bump layer needs inverting. I think you should also look at the settings in the specular layer, as it's a bit plasticy too.
• The images yu have used for the exterior are too flat and don't look like they are particularly good quality. Again, this could simply be texture settings.
• The books - the same few cover textures appear to ofen and the book cover texture is pixelating, meaning it's too small.
If you could fix those things, I think you would have a really cool image.