I know it's almost a cliche but the most important food book in my life is "The Joy of Cooking" by Marion Rombauer Becker, Irma S. Rombauer, and Ethan Becker. I'm actually on my second copy I now work off of the 75th anniversary edition---but I constantly go back to the---wait it's actually my 3rd copy--my first was a paperback ---that fell apart after many years--the second was a lovely white hard back copy that is now filthy and covered in years of spills and notes--that I constantly refer to. My first copy I started using in college --when I had only a hot plate to cook on and no experience cooking. I have made many recipes over the years, but I also use it for a guide--I may not want to make this recipe but I like the way they prepared the chicken for the recipe--or I want to try this sauce on vegetables instead of fish etc. It is one of the most inspirational cookbooks I've ever read---in that reading one recipe makes you think of better ways to prepare your own recipes. I highly recommend it! For all cooks!!!
For all you foodies there is a blog out there in the blogosphere called the gastronomers bookshelfhttp://www.thegastronomersbookshelf.com they have a giveaway going in which to enter you are asked to mention your most important food book--the prize is a copy of "Momofuku" if interested the giveaway is located here http://www.thegastronomersbookshelf.com/5314_book-giveaway-momofuku