I found this odd too. And the notion you could hide a Pratchett pocket book inside an open textbook. Anyone who has read Pratchett, or knows pocketbooks, knows this wouldn't work. They are voluminous (regardless of their name) and won't stay open on their own.

In fact, it seems a uniquely AI mistake to make to believe pocketbooks go in pockets. Anyone knows they don't fit, unless you have really big pockets and don't mind the weight and bulge.