I could easily read all the text on that demo page, even when looking at my monitor head-on.
Turns out, the 'secret' text is coloured to blend in with a white background, but the page doesn't actually enforce a white background; my light-grey background doesn't provide enough contrast to read a novel, but it brings out the 'secret' text nicely.
go to the demo page here: http://chrisharrison.net/projects/obliqueLCD/
look at your laptop screen from above and below (i.e., tilt or rock it) - not side to side.
More details here: http://chrisharrison.net/index.php/Research/ObliqueLCD