Since the first edition of this book in 1981, Prolog has continued to attract an unexpectedly great deal of interest in the computer science community and has turned out to be a basis for an important new family of programming languages and systems for Artificial Intelligence. In the preceding three editions, the authors have steadily added new material, improved the presentation, and corrected various minor errors to provide a textbook as well as a reference work for everyone who wants to study and use Prolog as a practical programming language. The authors concentrate on teaching "core" Prolog. All examples conform to this standard and will run on the most widely-used Prolog implementations some of which are listed in the appendices with indications as to how they diverge from the standard.
From the reviews of the fifth edition:
"This is the fifth and the most recent edition of a legendary book ... . It was probably the first introductory Prolog book and it is still the most gentle introduction to Prolog for everyone, including non-computer scientists. ... the book is as great as ever as an introductory text for Prolog. When a newbie asks for an introduction to Prolog, the best advice is still Clocksin & Mellish." (Bart Demoen, TLP-Theory and Practice of Logic Programming, Vol. 5 (3), 2005)