Alas, no, I've never seen anything like that.

It really ought to exist, right? Much as the Internet Archive and Google Books have unlocked a crazy array of knowledge by making millions of books instantly searchable, it would be extremely valuable to be able to search a subset of just the digital books one owns. Because it's a smaller grouping that was picked for a specific intellectual and cognitive goal -- i.e. books I personally liked -- search within that bucket could be enormously useful.

And of course, that'd require searching within a bunch of various ebook formats ...