I've owned a densitometer, and I agree that it's useful to use one for a while, particularly if you are trying to learn from books and don't have access to galleries of fine prints. If you take classes with a teacher who is really competent and can show you what a good negative looks like and how to get a good print visually, that's a perfectly good approach as well. Part of the reason that the Adams books have been so successful, I think, is that objective readings from a densitometer can give you an idea of what you're aiming for, which reproductions from books alone can't really do.