Last night at a Mac User group meeting I was giving the audience a run-down on the fnd.io website, which is an unofficial software search site for all Apple Stores. The next presentation was to be on Pages app on the Mac, so I chose to search for Pages.
The site quickly displayed the Apple app Pages for both iOS & Mac, plus several other apps with Pages in their names.
Then I went hunting for a particular book, which was found in very short order.
Some ratbag in the mob then drew my attention back to Pages with an inane question, so I searched for Pages again, but this time with the Books tab selected on the website.
Nothing was found, so I announced that there were limitations: You can't find Pages in Books.