Cooking, is it done?

Many factors affect baking times:

The temperature of the ingredients. Whether the pan is shiny or dull. The accuracy of your oven. (buy an oven thermometer and check at low, medium and high temps, note the results in your favorite cook book)

Since it's impossible to give exact baking times, a good recipe gives a range of time.

Check early.

A few minutes of extra cooking can make the difference between brownies that are moist and those that are dry and crumbly.

Or a roast that's moist and tender, and meat that's tough and chewy, simply because it has been overcooked

So cookbooks are wonderful, but there's much that recipes don't tell you about cooking.

Understanding how ingredients interact and the logic behind techniques helps you cook successfully.
Once you know what makes a recipe work, you can fill in the gaps yourself.

If you are already accomplished in the kitchen, understanding the science behind cooking is the ideal foundation for making changes and creating new recipes.