Like me, there are probably a lot people on here that have a lot of cookbooks, but I find I keep coming back to the same 1 or 2 books to give me the basis of most of the stuff I cook.
Mark Bittman's How to Cook Everything is my go-to all-purpose cookbook. The spine is now falling apart, though. It's quite amazing how many cuisines he covers. And there's now an iPhone version of the book, for extra convenience.
Mine is the Conran Cookbook - I must have/have had over 100 cookbooks, but this is the one that I've used most over the years, and has the most flour and sauce on it's pages.
Only maybe half the book is recipes, the rest covers things like equipment, basic techniques, identifying good ingredients, cuts of meat, etc.
In terms of recipes, it's not a book I look at for inspiration or adventure, but it's the book that I think taught me most about cookery. The recipes work, and don't seem to gloss over things - I suspect because the book dates from a time when most British cookbooks were pedagogic.
Recently, the one that has had the most use - Snowflakes & Schnapps - a book of Northern European cookery (Scandinavia, Germany, Baltic states and Bohemia).
this is a huge and amazing book that is really like an encyclopedia CIA's Professional Chef
The compilation books by Books for Cooks. Books for Cooks is a London based cook book store, with test kitchen. Every so often they publish a book with the best recipes to date, and they are all amazing.
Since I've just started to learn how to cook I've found Cooking Simply Everything pretty useful. The main focus of the book is to teach you the best way to cook individual pieces e.g the different ways to cook carrots. There's a couple of recipes thrown in there too.
Molto Italiano by Mario Batali is the one I keep coming back to. It's recipes are easy to follow and are relatively basic, but if you find decent to good ingredients, the food turns out great. I have loved just about every recipe I have tried in the book, although the baked ziti and the fettuccine Alfredo were probably the best tasting.
For South-East Asian food, Cradle of Flavor by James Oseland, is best book out there. It has a description of all the non-traditional ingredients, including tips on how to find them in the US. He even includes the Thai name for Pandan leaves, since they tend to be easier to find frozen, from a Thai manufacturer. The beef rendang recipe is amazingly close the versions I've had in Jakarta.
Due to my roots I keep coming back to the Cape Malay Cookery Book. It was at one point the most shoplifted book in South Africa. It contains most of the dishes my mother used to make for me when I was young and now I want to create them for myself.
White Heat (Marco Pierre White) is half autobiography and half recipie book which keeps me coming back.
Gorgeous Desserts by Annie Bell is my goto book for when Im entertaining and need a dessert - the pictures alone are wonderful.
Like other folks have mentioned multiple times, I'm partial to The Joy of Cooking.
I've also had good success using cookbooks from the Silver Palate:
- Silver Palate Cookbook
- Silver Palate Good Times Cookbook
- The New Basics Cookbook
Bill Granger's series of books are great, in my opinion. His recipes are easy, fresh and tasty.
The "ginger tea series" by James Barber:
These are three tiny cookbooks of simple, throw-it-together with what you have, recipes. Each recipe is illustrated in a one-page hand-drawn comic and they include entertaining and helpful tips (like which parts of the recipe you can go take a bath during). They consistently make yummy, fuss-free meals.
Have to agree with @Fredrik about Google. I would add YouTube for technique, especially when you are trying something totally new. Seeing a video of someone doing it is worth 1000 recipes.
Now for books, aside from the already mentioned reference books like Joy of Cooking, The Art of French Cooking, The Silver Spoon (I use the Italian version!), and Boston Cooking-School Cookbook I would throw in a couple of non-reference books that continually draw me back.
The The Greens Cookbook, really way ahead of it's time and a perfect balance of complimentary flavors in every recipe. Deborah Madison is a true master who understands food on a very deep level. Many of my favorite recipes come from this book and I have been using it for over 20 years.
Sundays at Moosewood Restaurant because it's like travelling around the world from your kitchen. Recipes from the heritage of many of the cooks at Moosewoods Restaurant. Actually learned to cook several new cuisines from this gem. Even wowed my Ethiopian friends. Another heavily bookmarked recipe book.
Ignore the fact that they are both vegetarian cookbooks. They are great cookbooks in their own right.
For Italian food my Italian copy of Science in the Kitchen and the Art of Eating Well is my first port of call; the Granddaddy of Italian cuisine.
For vegetarians, Mark Bittman's How to Cook Everything Vegetarian is an excellent all-around book I always come back to