I guess we are supposed to pile on, so I'll add that the author should read "The Art of Prolog" (Sterling & Shapiro) and then "The Craft of Prolog" (O'Keefe).

And also "Prolog Programming for AI" by Bratko and "Programming in Prolog" by Clocksin and Mellish.

Although these days I'd recommend anyone interested in Prolog starts in at the deep end with "Foundations of Logic Programming" by George W. Lloyd, because I've learned the hard way that teaching Prolog as a mere programming language, without explaining the whole logic programming thing, fails.