What is your all time favorite cookbook? I don't mean books about cooking (Heat, Kitchen Confidential, etc.), I mean recipe books. I know it's a stock answer, but Julia Child's The Way to Cook is probably my number one, with The French Laundry Cookbook right behind it.
Too many to count - but I still own my mother's well-used copies of Elizabeth David's books, written in the 1950s when the UK was coming out of austerity after the second world war and people were holidaying abroad, most for the first time - she introduced foods to the British palate which were new to most British palates... The books are just a happy memory of childhood meals.
The various Frugal Gourmet books by Jeff Smith. My oldest and best worn cookbooks. If it is for just one of those, then Three Ancient Cuisines (Greek, Roman & Chinese)
There are so many good ones that I have, but if I chose one it would be Jean Louis Palladin "Cooking for the seasons", primarily because I am a huge Jean Louis fan!
In 1971 I married a man whose family was born in Italy. I bought Mama Leone's Cookbook. My in-laws thought my "gravy" (spaghetti/meat sauce) was delicious. I passed that book along to my youngest son but I still make that gravy and still get raves.