French Cuisine (other than JC): Patricia Wells - Bistro Cooking,
At Home in Provence
Paula Wolfert - The Cooking of Southwest France (if you love ducks, that's the book for you)
Elizabeth David - French Provincial Cooking
I've also heard great things about Dorie Greenspan's recent Around My French Table, although reviewers note that as a contemporary French cooking has a lot of influences from around the globe (Asia, North Africa and even USA).
However, if you'd like to find out what French people are likely too cook at home these days, this has to be a great resource.
Spanish Cuisine
Penelopa Casas - The Foods and Wines of Spain, Tapas Portuguese Jean Anderson - The Food of Portugal Italian Marcella Hazan - The Essentials of Classic Italian Cooking Mexican Rick Bayless - Authentic Mexican, Mexico One Plate
At a Time Russian Anya von Bremzen - Please to the Table:
The Russian Cookbook German Mimi Sheraton - The German Cookbook: A Complete Guide to Mastering Authentic German Cooking Japanese Shizuo Tsuji - Japanese Cooking: A Simple Art Chinese Irene Kuo - The Key
To Chinese Cooking Barbara Tropp - The Modern Art of Chinese Cooking Thai David Thompson - Thai Food Indian Julie Sani - Classic Indian Cooking, Classic Indian Vegetarian and Grains Cooking Madhur Jaffrey - Indian Cooking, An Invitation to Indian Cooking, A Taste of India
Middle-Eastern Claudia Roden - The New Book of Middle Eastern Food
Greek Susanna Hoffman - The Olive and the Caper: Adventures in Greek Cooking Diane Kochilas - The Food and Wine of Greece South American Filipe
Rojas-Lombardi - The Art of South-American Cooking Copeland Marks - False Tongues and Sunday Bread Elisabeth L. Ortiz - A Taste of Latin America
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I too love Julia Child's book.
The Italian equivalent is without doubt "Essentials of Classic Italian Cooking" by Marcella Hazan.
She describes techniques and philosophies of the cuisine, touches on regional information, and answers the many "whys" about the idiosyncrasies of each recipe.
I can't recommend it enough.
cooking.stackexchange.com/users/1095/Ben M
Thai Food by David Thompson is one of the best regional cook books I have seen.
It goes into a lot of detail of the ingredients, methods and history of Thai Cooking.
I have had some great successes and
a few epic fails using it.
It can be too much for some, and it makes no compromises on ingredients so if you don't have an Asian store near by it may not been too useful to you.
cooking.stackexchange.com/users/1230/Jeremy French
This is a great book for Mexican Food.
http://www.amazon.co.uk/Mexican-Food-Simple-Thomasina-Miers/dp/0340994975/ref=sr_1_1?ie=UTF8&s=books&qid=1279568735&sr=1-1
This lady was in Master Chef UK and was a fantastic chef in the competition.
Not sure if it is a 'Mastering the Art Of' type of book, but she has some great ideas on food.
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Mimi Sheraton's classic The German Cookbook comes to mind - similar era, comprehensive, etc.
Diana Kennedy's The Cuisines of Mexico also.
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For Jewish food, The Book of Jewish Food: An Odyssey from Samarkand and Vilna to the Present Day is brilliant, with some lovely stories to go along with the food.
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If you love books on cooking that explain the
what and the why, here are two for you:
"On Food and Cooking" by Harold McGee "Cookwise" by Shirley O. Corriher
cooking.stackexchange.com/users/990/Mike Yockey
The Constance Spry Cookery Book. http://www.amazon.com/Constance-Spry-Cookery-Book/dp/1904010970
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For Szechuan cuisine, Land Of Plenty by Fuchsia Dunlop. http://www.amazon.com/Land-Plenty-Treasury-Authentic-Sichuan/dp/0393051773
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Marcella Hazan is probably the Italian equivalent to Julia: http://www.amazon.com/Essentials-Classic-Italian-Cooking-Marcella/dp/039458404X
Of course, Julia was persnickety in a way that Italians aren't.
Italians are picky about fresh ingredients, mostly.
cooking.stackexchange.com/users/982/Peter V
For Chinese, look at Betty Crocker's Chinese Cookbook , by Leeann Chin.
It's not the complete Tome like Mastering , but it will get you started.
I see there is a different tile, Betty Crocker's New Chinese Cookbook , which I take to be a revision, but I've never seen it.
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For Mexican cuisine, Rick Bayless's Authentic Mexican is tops in terms of breadth of coverage and detailed explanations of preparation methods.
You really get a strong sense of how food is prepared and consumed in Mexico, and some excellent instruction on how to prepare those foods in a non-Mexican kitchen.
I also highly recommend Rick Bayless's television program "Mexico One Plate at a Time".
In each episode he goes to Mexico and shows you how some dish or ingredient is used and eaten in Mexico, and then goes back to his kitchen in Chicago and shows you how to prepare a version of it at home.
Diana Kennedy's Mexican cookbooks are also highly rated, and I have one, but I didn't find it quite as engaging as Bayless's book.
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I almost forgot my other favorate cookbook of all time The Moro Cookook , this is by the owners of Moro restaurant in london.
It has two follow ups
but I think the first is the best.
While it is not as deep as some of the books mentioned here.
It has a good variety of north african influenced cuisine, with some tastes that all but the most adventurous cooks will find new.
cooking.stackexchange.com/users/1230/Jeremy French
If techniques apply, Mastering the Grill by Andrew Schloss ( Amazon Link ).
It's encyclopedic--covers all ingredients, preparations, timing, techniques, marinades, sauces, brines, rubs, cuisines, dishes, spices, trivia.
Plus it's very well organized and visually accesible.
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Jamie Oliver books are pretty epic when it comes to Italian and English cooking .
Though i highly recommend that you watch the videos instead :)
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Mastering the Art of French Cooking does a fantastic job of teaching what you need to do to cook all of the classic French recipes and why you need to do it the way that is recommended.  Can anyone recommend similar books for Northern and Southern Italian, Spanish, Mexican, Japanese, Chinese (Cantonese, Szechuan ...) ... etc?
I love "Mastering the Art of French Cooking". Can someone recommend similar books for other cuisines?
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Spanish: Penelopa Casas - The Foods and Wines of Spain, Tapas  Portuguese  Jean Anderson - The Food of Portugal  Italian:  Marcella Hazan - The Essentials of Classic Italian Cooking  Mexican:  Rick Bayless - Authentic Mexican, Mexico One Plate Russian: The Russian Cookbook  German:  Mimi Sheraton - The German Cookbook: A Complete Guide to Mastering Authentic German Cooking  Japanese:  Shizuo Tsuji - Japanese Cooking: A Simple Art  Chinese:  Irene Kuo - The Key, Barbara Tropp - The Modern Art of Chinese Cooking  Thai:  David Thompson - Thai Food  Indian:  Julie Sani - Classic Indian Cooking, Classic Indian Vegetarian and Grains Cooking  Madhur Jaffrey - Indian Cooking, An Invitation to Indian Cooking, A Taste of India  Jewish: The Book of Jewish Food: An Odyssey from Samarkand and Vilna to the Present Day Among the suggestions were Mimi Sheraton's The German Cookbook: A Complete Guide to Mastering Authentic German Cooking, Barbara Tropp - The Modern Art of Chinese Cooking and Susanna Hoffman's The Olive and the Caper: Adventures in Greek Cooking.
For Spanish cuisine, The Foods and Wines of Spain by Penelopa Caas. For Portuguese cuisine,  Jean Anderson - The Food of Portugal. For German cooking, Mimi Sheraton - The German Cookbook: A Complete Guide to Mastering Authentic German Cooking and Mimi Sheraton's classic  The German Cookbook. For Chinese cooking, Barbara Tropp - The Modern Art of Chinese Cooking, Betty Crocker's Chinese Cookbook , by Leeann Chin, Land Of Plenty  by Fuchsia Dunlop. For Greek cuisine, Susanna Hoffman - The Olive and the Caper: Adventures in Greek Cooking and  Diane Kochilas - The Food and Wine of Greece.   For South-American cooking, Rojas-Lombardi - The Art of South-American Cooking, Rick Bayless's  Authentic Mexican, Copeland Marks - False Tongues and Sunday Bread,  Elisabeth L. Ortiz - A Taste of Latin America and Diana Kennedy's  The Cuisines of Mexico. For Italian cooking, Essentials of Classic Italian Cooking by Marcella Hazan For Jewish cooking, The Book of Jewish Food: An Odyssey from Samarkand and Vilna to the Present Day.