My gf is the classic math-phobe, totally traumatized by math, etc., which surprises me, since she's whip-smart. The only explanation I can think of is that she got off to a bad start in elementary school.
My own love for mathematics was kindled by an old book on number theory that I found in my school's library. Unfortunately, I can't remember that book's title or author, so...
I'm looking for a very gentle first book on number theory.