[namelosw]

I recommend taking a look at 'Learn Datalog Today'[0] first. Although it's just Datalog (in S-expression form) which is a subset of Prolog but makes people get the gist of it very quickly.

For Prolog me too wondering if there's a great source. But I have read 'the Reasoned Schemer', it used a simple Scheme-based logical programming language for teaching purposes and it's very educative and entertaining.

[0] http://www.learndatalogtoday.org/