This book is a must for anyone doing serious Prolog programming. The book itself is a standard in clarity, concision and rigor.
There are minor drawbacks:
1. Poor paper quality and binding. Any programmer striving to write portable Prolog programs would use it heavily and the poor qualify shows off in just a month of daily use. Unfortunately, the form is not at the same level as the content.
2. The predefined predicates lack a listing by page (although they are listed by topic). This makes finding a certain particular predicate rather cumbersome when looked up frequently.
3. Minor typos.
Otherwise, no one serious about Prolog can afford to overlook this book.