Simply Maya User Community - Connect Node to Image File?

I don't have the book you mentioned, but i might know what you're talking about.

I might be wrong but I think you want to assign a specular file/texture node into the specular attibute under the selected material?

if that's what you want and assumming you have
1. an object
2. a material created for that object (blinn or anistropic)
3. and a mapped file/texture already under the material's color

then do the following:

Open up the hypersade window
1. Windows > Rendering Editors > Hypershade

2. In the hyper shade window, all of your materials in the scene should pop up

3. click once on the material node that you want to connect file/texture node to its specular.
(you should then also see the Attribute Editor box pop up on the right side of your screen as soon as you do this, if not already)

4. (in Hypershade window) hold a right mouse over that material node and scroll down and pick "Graph Network"

5. Now, in your "Work Area" still under the hypershade window, you should see (i think) at least a minimum of 3 different nodes (or more) linking to each other

6. of those nodes, find the node you want --- (i would say you want to pick the texuture file node) --- and hold down Middle Mouse Button to drag it out of the hypershade window and drop it into the Specular attribute, (which should be under the material's attibute in the Attribute Editor box)

Now your texture file node you dragged is connected to your material's specular attibute. if you wanted to connect the texture file node to your other file node that was mapped under the color, you would just drag it from hypeshade to that file's whatever atttibutes, but i don't think this is necessary if you are focusing on giving your material a specular look.

hope that makes sense and helped, if not forgive me :P