My only real gain from Nigella Lawson's books is the names she mentions as sources for certain recipes. This is the second book written by Anna Del Conte that I've bought, and I've also bought a book on muffins. Both Del Conte and the muffins were mentioned by Nigella, and all these other books turned out to be about ten times better than Nigella's. Lawson's recipes are not detailed, no description is provided on ingredients, tools to be used, cooking time and temperature (or if there is, it often doesn't have anything to do with what really happens in my own kitchen); the dishes I've cooked so far according to her recipes were very disappointing (at least to my own taste), and I keep wondering whether there's anything I do wrong (which I cannot ascertain, given the small amount of explanations Lawson offers).
This book is different. The recipes are not long, but are detailed enough (there is information on baking temperatures, exact cooking time and so on); there's a good introduction on key ingredients and kitchen equipment; the recipes are divided into clear steps and are nicely illustrated. When needed, there is also information on what to do in not very clear situations ("if there is too much liquid when the carrots are tender, uncover the pan and cook over high heat for 1 or 2 minutes"). Such details are, I think, essential for successful cooking. My own measure for success is the look and taste of the dishes, and all those I've cooked so far according to this book by Del Conte were very satisfactory.
Besides, the recipes give both metric and British measures, hurray (I never seem to be able to remember how many mililiters make a pint, and the like)!
I'm looking forward for the next book by Del Conte I have ordered and is on the way.