Ask HN: Has Google Books restricted in-book search?

I do a lot of searching of Google Books. I've noticed that in the last month or so, I'm seeing a lot more inside-the-book searches that give me a "no preview available for this page."

I even seen this when searching for terms that are literally on the page I'm previewing. They show up in my results list but still have "no preview available" and no page number.

Is this some policy change? A bug? I can't find any announcements about this. It definitely makes Google Books far less functional for me.

Of course, I'd love to live in a world where Google doesn't have this ridiculous pseudo-monopoly on book search. But this is not the world we live in.