My main copy of Joy of Cooking looks like it has traveled through a particularly messy war zone. (I also have an old 1950's edition I found in a used book store, once, and that makes interesting reading but not so interesting cooking.) I seldom actually cook a Joy of Cooking recipe, but it's indispensable as a reference or source of ideas.
Since I've gone all ketoriffic, Cravable Keto by Kyndra Holley and Keto Instant Pot by Maria Emmerich have gotten quite a workout, though I've learned that any time Kyndra says "1 teaspoon onion powder" 1/4 teaspoon will be quite adequate -- the same with her and garlic powder.
Not really a cookbook, but I've also repeatedly watched my Great Courses classes from Culinary Institute of the Arts -- they're solid gold and teach you how to cook without a recipe. (People reviewing the course have gotten their panties all in a twist because the courses don't tell you things like "1/2 teaspoon salt" -- I think those folks sort of missed the whole point. First time that ever happened in on-line reviews ....) I especially recommend any course by the late Bill Briwa, an amazing teacher. They had a really great sale on a couple of the courses, so I thought I'd get a few "good tips" since I had been cooking fairly seriously for dang near 50 years. Color my mind blown, 'cause the guy totally reworked how I think about a meal.