Why not just upload a text file into the phone?

That's definetly possible, but may be less convenient.

First of all, you'll probably need a special reading software -- you don't want to scroll the text to the point where you've left it last time, do you? Besides that, standard "notepad" applications on cell phones may not produce the optimal text layout for the small screen.

What's more, with downloaded books you have to store the whole text of the book in your phone's memory, while with tx2ph only the pages you're reading right now (the displayed page plus the cached ones) are downloaded.

And since the phone's built-in WAP browser is used, you don't need to install anything (wasting memory you'd rather spend on an extra ringtone ;)), don't have to worry about compatibility.