It sounds like the site is not rendering correctly for you. The font size itself is (supposed to be) very large, so if you are zooming in, then it sounds like something's wrong. (Mobile device, maybe?) If anything, some folks might prefer to zoom out, not in.
As for the 2/3 empty white space, that is an attempt to have a measure (line length) [1] that is readable. A general rule of thumb is somewhere around 70 characters per line is comfortable to read for single-column text. Now, I tend to think that 70 characters per line feels pretty short on the web... in my personal experience, around 100 characters feels a lot better.
Anyway, if you're interested in typography, take a look at Bringhurst's The Elements of Typographic Style.
As for the 2/3 empty white space, that is an attempt to have a measure (line length) [1] that is readable. A general rule of thumb is somewhere around 70 characters per line is comfortable to read for single-column text. Now, I tend to think that 70 characters per line feels pretty short on the web... in my personal experience, around 100 characters feels a lot better.
Anyway, if you're interested in typography, take a look at Bringhurst's The Elements of Typographic Style.
[1] https://en.wikipedia.org/wiki/Measure_%28typography%29