figuring out materials & maps

[cakewalkr7]

When I work through tutorials that cover materials in max, rarely do they mention why I'm setting a certain value or choosing a shader or map. I feel that I'm doing well at basic modeling, but when I try to create a material, I'm just not sure how to create what I have in my head. For example, I wanted to create a wallpaper material that has a random vein pattern to it. I played with different procedural maps but I wasn't able to do it. In this particular case, I couldn't figure out how to blur the vein and make it more random. But my main question really is just whether some of you could recommend a good book or web site w/ tutorials on creating realistic materials? Also, do most of you create your own textures/materials or is it more common to just use something from a collection? Thanks.