Peter Norvig also has two implementations of Prolog in Paradigms of AI Programming (first one is interpreted, second is complied) in Common Lisp. The book is highly recommended because Norvig's code is very elegant and his exposition is wonderful.
Allegro Prolog [1] is based on Norvig's implementation, although I'm sure they've done a fair bit of optimizing.
You should totally do it... it's fantastic. Norvig makes it quite clear in the beginning that he expects you to know atleast some lisp beforehand (the "intro" chapter is a bit sparse), so you might want to brush you on your CL skills before you dive in.
Allegro Prolog [1] is based on Norvig's implementation, although I'm sure they've done a fair bit of optimizing.
[1]: http://www.franz.com/products/prolog/