Those are useful distinctions - and seem very clear to me, thanks! The book that prompted the query is Margaret Mahy's The Catalogue of the Universe, in which a popular astronomy book called The Catalogue of the Universe plays a part. To make it interesting, though, there really is a popular astronomy book of that name (minus the first definite article), which appears from its date and general description to be very much like the one mentioned in Mahy's text.