What causes odd deformations when using Subsurf? first time here.

Alrighty, I'm quite new to 3D model design in Blender, but I have a little problem with my book model. The mesh is fine (I think). But there are a good few points where the text mesh goes wrong for some weird reason. If you need to know which version of Blender I'm using, it's Blender 2.69.

When I apply the "subdivision surface" modifier and set the subdivision render to 2, the faces go in and deform in certain areas. As far I'm not sure what is wrong at this point. I've taken two pictures just in case you need them. 





Take note that I'm still unaware of some certain tools and common knowledge in Blender, go easy on the in depth reasons and fix details. Just simplify it please :) 

Blend file :  http://www.pasteall.org/blend/30527
You have some issues with the topology:


Extra edges on the large inner-top face, creating n-gons (also see this question):



To fix them, select them and press Delete > Edges.
Extra vertices on the edges, also creating n-gons:



To fix them, select them and press Delete > Dissolve vertices.
Internal edges on each corner:

 

To fix them, select them and press Delete > Edges.
Double vertices one of the corners:



To fix them, either merge them manually, or select everything (or just the area you want to check for doubles, but in this case it doesn't really matter) and press W > Remove Doubles.
No face on the top loop, creating non-manifold topology:

It's a bit hard to see, but if you select it with AltRMB and translate it, it's a bit more obvious:



You can select non-manifold geometry with CtrlAltShiftM.


Example .blend