Thing is, there are plenty of books that are called "comics" for various reasons, such as Maus, compilations of weekly publications of a non-strip serial (e.g. tankobons)*, and some other cases.

*compare to how many classic novels, e.g. work by Charles Dickens, were initially published chapter-by-chapter but are now read as compilations. Many manga as well as western comics also get published this way (e.g. I have an old Daredevil book that was originally published on a monthly basis but reads just fine consecutively as a unified book)