You might want to add The Reader's Guide to the Encyclopaedia Britannica, PD text available at https://www.gutenberg.org/ebooks/74039 and scans at https://archive.org/details/readersguidetoen00londuoft - It would fit naturally with the Ancillary material that includes the topic-based index.

It would indeed. I will see about working this in, it's highly pertinent.