Very, very cool. Hats off. I've considered attempting a more limited form of this for years.
For those who don't know, the 1911 Britannica is heralded for several reasons (and rightly criticized for regrettable others), but the most well-known is that it was the last encyclopedia before The Great War, and hence had a good amount of steam/optimism coming from the first and second industrial revolutions and the "Progressive Era", not sullied yet by thoughts of "the war to end all wars".
Trying https://britannica11.org specifically, it quickly found and displayed the article I searched for, chosen (to search for) at random: Portuguese East Africa, at https://britannica11.org/article/22-0177-portuguese-east-afr...
A question/idea for nice-to-haves, most respectfully. I don't know if it would be feasible. It's probably perfect as it is, simply linking to the image-page in unobtrusive text for each section. But I would love an option (emphasis on option) to see the text side by side with the page images. That parallel view would load all of the page images on the same page as the full article text. That way, I could "confirm" or "fact check" the faithfulness of the OCR, and also see the beautiful printing, at once, without opening each page separately and managing the images/windows myself. Most likely, I would use the site to jump to the articles, and read them mainly as images, only switching to the text form to verify what something said, or to copy-paste cleanly, etc. (As it is, initially, I thought I read the original images were available, but had to visit the page three (3!) times before finding where the side-links to them were.) Maybe thumbnails could be a middle-ground option (again, optional) for salience.
Very, very well done. And it's fast!