A series of unsuccessful (and unrelated) searches led to the happy result of finding this book (and the site it’s on). The Public Domain Review is a fascinating collection of articles about (and a collection of) out-of-copyright texts, images and films, and somehow I’d never seen it before.
I’d seen a page from the book and thought it to be something quite modern, something produced by some later follower of De Stijl or Bauhaus (something the Public Domain Review also comments on), but it is in fact from 1847. Not something you’d associate with early Victorian publishing at all. It’s a remarkable book, and thinking back to when I first learned geometry I wondered if something like this would have helped. In all honesty (and of course entirely my opinion) I can’t say it would. The pages are a visual delight but they compel the learner not only to learn the concepts and mathematical language but a whole new graphical one too. From my memories of Euclid you need a good guiding commentary (or a good teacher, or both) rather than a new translation to help you make the necessary connections and learn the principles well.
The long-s characters and the ornamented capitals are a clue to the age of the book, but the diagrams appear very modern.