Well, I do cook from them, using 2-3 recipes at least once a week. It's kind of like a tourbook I read 6 months before visiting a new destination. I like to anticipate. Most of the cookbooks are usable. I can get Mexican or Asian ingredients with little difficulty. I have no luck with a Caribbean cookbook that seems to call for ingredients I've never seen or tasted.
I like my Joy of Cooking. I've only had it a year and prefer it for basics to any of the other standards. I also have trouble with seafood recipes, especially from Mediterranean countries. I don't know if I can really substitute catfish for everything else.