Sorry but I've been busy and, frankly, forgot about this thread.
I'm not much for schools but I did take a few classes in an art school and I often tell people to go take a design class. The best money I ever spent. Of course the professor you get has a lot to do with how much you will get out of it too. Seeing the reactions of professor and classmates made understanding the concepts a lot easier than if you were sitting alone at home with a book.
But I have been looking for a book myself so as to have something to suggest to those who can't afford a class but I have yet to find one.
I do not like photo books on composition. They leave a lot to be desired because they leave a lot of stuff out if it's not directly related to photo. The problem is I have found that a lot of that stuff is useful to know and understand. A general design class is a much better bet.
That said, the basic theory in art is that anything goes. Accept that first or you will have problems. It doesn't mean that you have to like everything, it only means that if you like it that is enough. When you mix art and commercial work you of course have to take your client into consideration. Some will allow you to be very artsy, some will not.
By the way, few people really understand PHI, the Golden number/ the Divine Proportion. I get some of it but, to be honest, everytime I reread my book on the subject, I find I got some of it totally wrong.
Here are two books that may help you:
"
Divine Proportion/PHI" by
Priya Hemenway. The only one I kept from the bunch I got to study the idea, I thought it was the best.
"
An Introduction to Color" by
Ralph Evans. This is a pretty old book so may not be easy to find but it is very good. It was published in England too btw when it came out in 1948. Understanding color and how they relate to each other and how they play on the eye is primordial in any artistic endeavor. Including B&W photography, because it allows you to know what shade of gray a color will convert to.
In the meantime, look at art, look at art, look at art. And always try and figure out why you like some stuff, why you dislike other stuff. And of course doing so in a gallery is a much better idea. Unfortunately most affordable art books are pretty poor reproductions of the works and really do not give you a good sense of the works.
Hope that helps.