A great cookbook is one that can provide useful information, tips and techniques to help readers become better cooks. It should also have a variety of recipes that range from the simple to the complex. A good cookbook should also include helpful illustrations and photographs, nutritional information and clear instructions. Additionally, a great cookbook should offer an interesting writing style, providing readers with interesting anecdotes and stories as well as helpful advice. Finally, a great cookbook should feature a wide selection of recipes that appeal to readers' tastes and dietary needs.