CategoryBook is for a page describing a book. Click on the heading for a list of the entries.
See also: CategoryBooks which is slightly different.
BookShelved may be of interest to folks discussing books.
I often find WikiPages on books to have very little information aside from ISBN, and have repeatedly suppressed my urge to delete these useless entries.Example of a useful book listing: See link at GenerationsAtWork. Book listings should have material stimulating to a casual reader as well.
Here are some pages which contain CategoryBook, but do not have an ISBN. WikiGnomes are hereby notified
HitchhikersGuideToTheGalaxy: Wasn't sure, if the other ISBNs of the trilogy should have been listed as well. So I kept it in this list.