Lots of good information about the first 4 books is presented. I really enjoyed reading about Diana's writing process as it provided valuable insights into how she crafted her stories. Additionally, the Gaelic information was fascinating and added an interesting cultural element. However, it should be noted that some of the information is repeated in different sections of the book. This can be a bit distracting for the reader. Overall, it serves as a better reference guide than a sit-and-read book. It allows readers to quickly look up specific details and facts. Despite the repetition, the wealth of information makes it a useful resource for fans of the series.