Here is a pair of blow-ups from the sample page.
Here is a 200% blow up:
This 200% enlargement shows what you see with the "High Res" chapters of the eBook. The file appears at this resolution and carries the entire eBook as a continuous stream.
Let's get REALLY close:
This one is 400% and shows how big you can blow-up the page with the Ultra-Resolution version of the eBook. Notice that you have not yet run out of pixels in the image. It's as if your face were almost touching the page--if your eyes could focus this close on an actual paper book!
Note also, that the page here is deeply compressed for quick Internet viewing, and the images in the eBook use much less compression.