Paul and our development team did a magnificent job putting everything into the book. Your job, should you decide to accept it, is to pull everything from the book, make sense of it, and use it.
The audio course gives more structure and offers a way to learn PhotoReading without having to read. Many people, before they learn PhotoReading, have challenges learning from books.
The seminar has structure, plus a task master show has mastered PhotoReading. Your instructor is a great resource to help ensure you take home everything you can.
All three are good.
If you have plenty of time and plenty of money, do all three. You will get your time's and money's worth.
You will also receive a lot of benefit by revisiting the book or the audio course or the seminar again in six months. You will be reapproaching it from the perspective of being a PhotoReader, which will help you take your skills to the next level.
Best of all it is free. It will only cost you time to revisit the book or the audio course or the seminar (repeats are free in the US).
I've sat through dozens of PhotoReading classes over the years (and I typically do not like classroom situations). I received so much benefit and insights from listening to the students. That's one of the reasons our instructors are so good--they constantly are exposed to the experiences of their students.