Books or Power Wheel?

Is the power wheel worth the money? I was wondering whether to buy that or get a couple of books from Ironmind - Rock Iron Steel and Powerlifting Texas Style

The Power Wheel is defintely worth the money! In addition to working your abs, you can work your upper body, legs etc. Lot of cool exercises that you can do with it.

I just use a standard bar with a 25 on each side, and it seems to work well.