Solid gold. I just finished this book (pretty much in one go it was so engaging). The author does a great job at walking you through his creative process with plenty of examples, honesty, and bits of wisdom. About 20 pages in I realized I needed to be taking notes and ended up with a full page gems.

Even if you don't intend to publish adventures, this book will help you homebrew your own worlds for your table. It will even help you spice up published adventures. Again, solid gold. If you DM regularly, read this book.