[Jellby]

That looks fine.

But consider that the document might be read in small screens or with large fonts, so maybe:

(a) Using absolute units (125px) might not be a good idea.

(b) "Wasting" valuable space in the right side just because some name will appear there from time to time might look not so good.

For an e-book, I'd probably use some other style, like putting the character names in their own lines (paragraphs), or just writing them in bold, with some space to set them appart from the text. It won't look so pretty, but it can be more readable in a wider variety of systems.

When you test your code in a browser, resize the window to simulate a smaller screen.