It's not the speed that matters, it's that you do it.
Either way, this is a fun challenge. I now know that I read 769 words a minute and I could read The Grapes of Wrath in 3 hours and 40 minutes (it sure seemed torturously longer than that in high school).
Source: Staples eReader Department
Thank you to I Have Seen The Whole Of The Internet for bringing this test to my attention.
Thank you also to Staples for their innovative e-reader marketing.