'Cook's Illustrated: The Science of Good Cooking'
You follow recipes to the letter, have "Joy of Cooking," but are stumped by the occasional culinary failure. Consider this book. In addition to 400 recipes "engineered for perfection," its focus is on culinary "whys." Instead of appetizer-to-dessert chapters, you have "Concepts," as in "Slow Heating Makes Meat Tender." Sidebars ("Practical Science: Chicken Safety," "Why This Recipe Works") plus explanatory visuals pepper the volume, making it more accessible than some other science-focused books.
America's Test Kitchen, $40