The advanced poro book introduces many more complex shots. Multirail position shots, more advanced safties. It has alot about the mental game and training to advance your game. If your game is on the improve it is really one of the best books available for an advanced amateur. You will see that so many instructional books start at step one:stance, grip, stroke...this one starts with the premise that you already have a strong game and shows you how to play even better.
BTW I do have both copies of the books and would sell you both so then you don't have to choose. I could do $50 delivered in the continental US, payment by Paypal accepted. Just PM me and let me know if you want them. Good luck with your game.