[GregBuchholz]

Chapter 4 of "The Art of Prolog" ("The Computation Model of Logic Programs") is about that very topic. It doesn't go into gory details on how to optimize an interpreter for fast execution, but it does go into enough detail that I was able to create a Prologish interpreter in ~30 lines of Haskell many years ago. Apparently "The Art of Prolog" is a free download now (there is a PDF link on the left side of the page).