Though I may work directly with XML very little, I want to begin the process of learning it in conjunction with FrameMaker.  I've already read XML in 24Hours, which was nearly a complete waste of time.  The book focused far too much on the Web and very little on anything specific.
I am looking to learn as much about writing well structured XML code as possible.  I am in publishing, not coding, so my aim is really to create portable, usable content, not delivery systems.  I may never write a DTD, but I'd like to know how to append one to make it fit our organizations needs as well as possible.  
So, where could I find information about this?  I'm headed back to the library to again pilfer their tech shelves, but are there any books you would recommend for this sort of thing.  I realize this isn't specifically a question involving development, so much as using a mark up language for its original intent--marking up--but, any help you could give would be greatly appreciated.
			
		