I feel the same way about starting out with photography as Chris. In many ways I think I was lucky to start photography way before digital photography even began. My first camera, and most that followed it, was a manually operated device that required me to learn about light and how to gauge a camera to read it. It must be very confusing to start out with these complicated digital devices today that give you too many choices and do too much for you.
I do think that some time learning how to use your new digital camera is very important if you want good results and to be able to control it, but I think, as Chris said, it is as important, if not more, to understand light, composition, animal behavior (if you want to take photos of animals, or even plants!), and interpreting what it is that you have in your mind's eye.
I have read all of Galen Rowell's books and Chris is right about the insight and knowledge they offer. He tends to be a mountain and sport photographer, though, and my preference has always been for animal and plant photography. The best books I have found have been those of John Shaw: John Shaw's Nature Photography Field Guide , John Shaw's Landscape Photography, John Shaw's Closeups in Nature (Practical Photography Books). The knowledge in them and the ability to get it across very clearly are Shaw's strong points. However, they are not about digital photography and therefore don't consider such topics as white balance and the differences in focal lengths (compared to 35 mm film lenses) and megapixels and the use of Photoshop. Nevertheless, twenty years later I still refer to these texts when I get confused about light or finding my own way of seeing things.
But, what truly helped me to understand nature photography was to look at many different examples of photographers I love (not just nature photographers): Ansel Adams, Edward Weston, Henri Cartier Bressan, Ernst Haas, John Shaw, David Meunch, Sebastiao Selgado, Tom Mangelsen, Jim Brandenburg, and, a personal friend of mine, Pete McGregor from New Zealand, to name a few. Just looking at them will help to inspire your own vision.