Armageddon, by Stanley Waterloo, is another Rand McNally title with a W. W. Denslow cover. This book's cover is very simple, and at first glance doesn't really make me think of Denslow, other than the lettering which is in his typical style. This was published in 1898, the last year that Denslow designed Rand McNally covers.
But, this is another title with a poster designed by Denslow, viewable at the New York Public Library website. When compared with the poster, it becomes clear that this is indeed a Denslow design. The same cloud profiles are used as the cover motif, and the setting sun on the poster is the main element on the spine of the book.