Absolutely brilliant formatting, thanks!
I have the world's smallest nitpick; the ludovico font doesn't seem to contain hyphens, search for "Over on the back the same hand had written this further information" and look at "Spy-glass" in the letter underneath. You surely don't need instructions, but to me it looks best to add
to CSS and of course replace hyphens in the relevant divs with "<span class="ludohyphen">-</span>".
This case is a trivial s/r, but I have a related question: If i find errors in an epub, do uploaders accept a corrected epub, or do you prefer a list of errata (so you don't have to depend on the ability of random strangers to edit epubs)? I couldn't find comments on this in the guidelines. For me personally it might be easier to just make the changes than to compile a list of errata.