Tofu helps address the common problem that people don't like reading text on the screen. Why is that, anyway? I believe there are two main reasons: line width and visual instability. Text is usually very wide on the screen, which makes going from the end of one line to the beginning of the next difficult. That's why newspapers have narrow columns: It makes them faster to read.
So why not just take a normal window and make it narrower, scrolling down as you need? Well, there are usually a lot of lines in a text, and all look more or less the same, so if they move past your eyes vertically, they are difficult to keep track of. The text doesn't feel stable, and you get lost easily.
In Tofu, text is arranged in columns, and each column is only as high as your window. So lines are nice and narrow, they don't move about vertically, plus your text is now in easy-to-digest chunks. You just scroll from column to column horizontally, and feel more in control.
Tofu also includes some other useful features to make reading easier for you. You can jump to any point in your text by simply typing some letters near it (without choosing any command first). There's a "View In Columns" service so you can, for example, grab some text from a Web page. And it lets you use your voice to navigate text, so you can literally sit back and read.