Reading a book about cooking, reading a cookbook, reading a cook book, and reading a cooking book could potentially be four different things:

1. A book about cooking is generally an instructional book or informational book like a textbook, book on the history of cooking, etc. Other than the above list, reading a book about cooking that may inform you about your culinary skills. Is there a cooking course and the cooking shall be the focus?
2. What’s cookbook? Is it really a cookbook? Is there anything other with recipes and inspiration?
3. A cook book is somewhat awkward, and might want to be avoided, as there’s the chance it could be interpreted as a book about cooks rather than cooking or recipes (at the very least it’s ambiguous)
4. A cooking book is even more awkward, as it could potentially bring to mind an image of reading an uncooked book which is sitting in warm water simmering with the stew.

How did you see it in life?

A kitchen book is called a recipe book. In its general terms a recipe book is

called a cookbook.

I like a cooking book, but why? Is a cookery book fine without an hyphen, and without space?