The most helpful book about personal style that I've read so far is this one:
The book approaches style from the perspective of art. Using many illustrations from famous paintings of women (usually nudes), as well as charts and diagrams, the authors show that all body types are just that: types--not problems or flaws--and all are beautiful. The key to showcasing your personal beauty is in the art world: proportion, line, and color.
With the authors' help I began looking at my body as a work of art, a sculpture or a painting, and I began to understand the basic principles behind why certain clothing shapes and designs work or don't work on me. It's a matter of proportion. Just as in art, there are certain lines and proportion that are generally pleasing to the eye, and the closer you can get to that, the more pleasing your form will be to others. And it's not a matter of the "in" body type this season; it's a matter of working with the proportions of your own body.
There is also a whole section on color, with pages of color swatches that you use to find your own personal palette of color. I did this exercise with my daughter and we each ended up with a little key ring of color cards of our "colors." The difference from other color theories being that in this case the colors were truly MY colors: the four colors of my eyes (the iris, the ring around it, the specks, the whites), the two colors of my hair (the base color and the highlights), the two colors of my skin (the actual skin color, and the undertone), rather than a set of colors that are supposed to look good on me. The idea behind this is that you will then find colors to wear that enhance the colors of YOU. This actually works. I have found that my eyes, instead of being green are actually two shades of gray that look green from a distance. This is why certain shades of gray seem to make my eyes bigger and prettier.
The last page of the book has an unexpected quote that sums up the philosophy of the book:
For thou didst form my inward parts; Thou didst weave me in my mother's womb. I will give thanks to Thee, for I am fearfully and wonderfully made. Wonderful are Thy works, and my soul knows it very well. Psalm 139:13-14