hi, mike, glad for your interests.
First, "周公解梦" is not authored by the Duke of Zhou. It is a book from posterity, people just use his name to sound more convincing. I've skimmed over the book before, not quite reasonable for me.
Yi-Jing, actually there are three been written but only one has been hand down till now which wrote at Zhou Dynasty, also known as '周易 Zhou-Yi'. It is the source of Chinese philosophy and culture. Because it was written in very early time, Kong fuzi also wrote some explanation for it. I am afraid it is too complicate for foreigners, but good luck for you and wish help a little bit :)