If I had to reduce my 45-50 cookbooks to just one, this would be it. Cliche perhaps, but true. I have the 1997 edition (pictured here); it was the first major update in decades of this cooking "bible." There were a number of international and vegetarian dishes added. Unfortunately, the editors took out some of the old-fashioned information and recipes, such as a chapter on canning, but I've heard that the 2006 edition puts those items back in--the best of both worlds. I don't know whether I'll take the plunge and get the newer one or not since my current one is all "ripply" on certain pages where various ingredients have jumped onto the page while I've been diligently following a favorite recipe from the same page.
Joy of Cooking is a classic for good reason. It's the place to go when you have a strange ingredient and want to find recipes to use it. It's also the place to go when someone wants a traditional pound cake, an Indian samosa, chicken pot pie, or stuffed grape leaves. Truly, there's a little bit of everything in it! It can be a bit labor-intensive at times, but everything "works"--a cookbook you can trust. If you're trying to reduce food costs at home, consider an all-purpose cookbook like this since it also includes recipes for making your own bread, white sauces (think, condensed soups), cookies, granola, etc.
I think every cook should have one of these, at least for reference! You can probably find them easily in a used book store since they're fairly ubiquitous.