I don’t have much for book recommendations, but start off with The Elements of Typographic Style [http://www.amazon.com/Elements-Typographic-Style-Robert-Brin...] and get a feel for creating usable and readable typography in your apps. http://www.typographyforlawyers.com/ makes a good companion site too.

Graphic design comes down to “the art of organizing” and effectively using five elements: line, shape, space, colour and texture. When searching for fundamental design books I’d look for those that cover how to harness said elements effectively.