You can now ‘search inside’ all 4m Open Library books held at Archive.org, with your search seemingly constrained to just those books (and not the jumble that Archive.org also hosts). Nice results, with multi-snippets from deep inside the full-text of the books, plus phrase highlighting. This looks like excellent work, and it takes advantage of new tweaks by Archive.org’s search leader Giovanni Damiola.
A serious history researcher is still going to need to pound Archive.org itself and go through everything, but at first glance this seems to be a useful time-saver for those who only need to search the upper layers of the service.
The ultimate goal of the Open Library is “One Web page for every book ever published”. Think of it as one of those annoying university repositories where 95% of the full-text is not available yet, but will be one day… so “here’s a record page instead”. But in this case it’s for all books, and already has a substantial amount of full-text for free.