I'm having a hard time trying to get my head around the fundamentals of gauge theory. I've taken classes in QFT and Particle Symmetries recently, both of which touch on the topic, but neither explained it in detail. Browsing the Wikipedia entry on gauge theory gives me the same heuristic arguments I've read hundreds of times, together with some mathematical formalism that's totally impenetrable.

Does anyone know of an introductory book that will explain gauge symmetries, the gauge group and their applications to a grad school student? Ideally I'd like a book which starts slowly but gets far, and isn't too basic. However I'm not looking for a text where you need to have done a couple of courses in differential geometry (fibre bundles etc) to get started!