If you have at least one other sim in your household, you will also have a new option for 'Group Cooking' when clicking on a the cookbook, a counter, fridge, or stove. You can find the cookbook in Appliances > Kitchen Appliances. There is also a cheat that allows you to learn locked recipes if you shift+click on the cookbook.
If you have the Cats & Dogs or Cottage Living Pack or my Cowplant Farming mod installed, then you'll find a menu for Animal Food as well. There is also a menu for Drinks that can be made at the bar as well as a section for making fresh Ingredients like bread and pasta. In addition to that, you can find recipes by Region or by Special Diets, and you can even choose recipes based on the current season you're in! All recipes can be found in at least one category in the 'Cook by Category' menu. After organizing them into categories I realized it looked pretty empty so I went ahead and added all in-game recipes to it as well. I made this cookbook object so that there would be an easy way to find all my custom recipes.