I've not heard of the Purity Cookbook. I'll have to check that out. I did find a Mc Call's cookbook for her. It is not hugely collectable, like Julia child's books, but my grandmother gave me a copy that she no longer used and my dau and I still make all kinds of things out of it. It has the best pies ever. I even bought myself another copy, because mine is barely holding together.
Another cookbook, that I'm looking for is, Stocking Up, by Rodale Press. It's a classic, "back to the lander," type of book and was written by the people who started the organic gardening movement. I have a copy. Maybe I'll just give it to her.
Martha Stewart is also on my list. There is a site called, "The Cookbook Village," that gives lots of good information about collecting cookbooks.