Matthew, below are a few links to some easy introductory material on sensitometry/densitometry from Kodak. It will give you the basics, definitions, etc. The Zone System in Adams's The Negative is essentially a simplified introduction to applying some of these ideas to your own film exposure and processing with the desired final print in mind. It is nothing more than that. Adams does a good job introducing the basic concepts, but the Kodak publications might help.

In addition, I've included a link to a brosder set of Kodak and Ilford resources I put together (the sensitometry workbook is one of them). Some of these publications are aimed at helping less experienced people gain an understanding of things like ISO vs personal exposure index (which ends up being part of the Zone System), etc. Stick with this stuff before getting everyone's opinions. Re-read Adams.