One of the problems with quantum theory is that is usually the version from the 1920's which is talked about, but this doesn't answer many important questions concerning the interaction of light and matter. For that you need the more advanced quantum electrodynamics (QED). So how can you find out about this vital subject without spending many years doing graduate level physics? Well QED
by Richard Feynman would be an excellent place to start. It's based on a series of lectures he gave for an audience of non-physicists. Hence a lack of previous knowledge of the subject shouldn't be a problem - provided you're prepared to do a bit of work in following his explanations.
The book consists of four chapters. Despite all the quantum talk, the first two chapters really deal with classical wave optics, but in a non-standard way. The advantage of this approach becomes clear in the third chapter, when a few modifications lead the reader to the power of quantum electrodynamics. The fourth chapters looks at some 'loose ends', including renormalization and QCD - the extension of QED to deal with nuclear physics. The book provides a neat way of explaining a difficult subject to a non-technical readership, although I'm not so convinced about its usefulness for those who already know a bit about quantum theory.