I recently attended the Photoreading seminar. Before reading the seminar, I picked up the book and started working with it. I actually started getting results from the system before I went to the seminar, and, in my honest opinion, I think that if one applies him/herself to the system (using the Photoreading book alone) you can learn the system phenominally.
I actually found the seminar to be more of a coaching session, but I really learned nothing more than I knew already from the book.
Therefore, I would purchase the 3rd edition book, and commit to using the system, and save some money for yourself to eat and what not. If you need coaching, the people at Learning Strategies can answer any of your questions.
The key to learning the system, though, is to realize that each of the techniques is a self-contained reading technique that has been used and researched in other systems. The photoreading step is actually (imho) the only truly "unique" part of the system (which is essentially the hinge). Definitely use the book confidently, knowing that it works. ;-)