The cookbook part is funny but a cookbook is not a banned book in the way people usually mean. Banned books are things like novels or memoirs that got pulled from schools and libraries because of the ideas in them, not recipes. Your grandma probably just had a cookbook that went out of print or got recalled over a bad recipe, which is a whole different thing. There are a few cookbooks that got pulled for stuff like unsafe canning steps or plagiarism, but nobody was banning them for being dangerous to the mind. So she may have kept a rare or recalled cookbook, which is still a good find, but it is not quite the same shelf as Slaughterhouse-Five.