Sorry this is a late reply, but thought I'd chime in anyway. I'm still pretty new to all of this, but I'm learning. I own two copies of Dr. Christopher's book, the recent (2009) centennial edition (bought a new copy from ebay at about half price), then I bought an old second printing 1977 edition from amazon (still in excellent shape). (Another great source for used is half.com, which gets overlooked and may have a lower price).
Real reason for posting: I only bought one other herbal, but it was for identification purposes in case I am ever forced to identify the plants on my own. From what I can see, you will probably need to buy several if you really want to get serious about it, and your not already a botanist or someone raised in the great outdoors (I'm a city guy). I bought a copy of "National Geographic's Desk Reference to Nature's Medicine." I bought a used hardcover for cheap. I'm posting links to the HC (2006) and paperback (2008) below. Each herb is shown in a photograph and a line drawing (instead of one or the other), although I wish the photograph was larger. Anyway, it's practically worthless for healing, but that's not what I bought it for. (Some of the articles might make for good rainy day reading).