This is a book about creating a Sandbox style game. It has many examples and details about the homemade campaign of the author, also, and Is very opinionated about the virtues of a sandbox game. It has some value to any who will create a sandbox game and have interest to see the solutions taken by the author.
The PDF version doesn't have any bookmarks, at 8 euros I think is overpriced. Also, considering it's technically a text book (With many tables, also not bookmarked nor hyperlinked), I think hardly deserves be a pdf and not an .mobi or epub ebook.