Mr Red wrote: I have a plan to do one more wrinkle - to include possessives in the search

Do you mean to allow the user to type in an apostrophe? That seems like an unnecessary complication to me. I can type horse and it suggests horse's, which I can select.

I would actually loosen up the search. It someone types horse, or selects horse, I would implicitly include horses, horse's, and even horses'. If somebody is looking for memoires about horses they're likely to be interested in any of those.

Apart from the delimiters you allude to there are the complications around glyphs for the possessive apostrophe. horse's horse’s and horse‘s are all different, and which one is in the title may depend on who typed it and using what software.

It works and plays OK on Firefox/Android BTW.