Introductionary literature

Hi!

I'm looking for tips regarding introductionary literature for music 
theory. Personally I have basically no background in music aside from 
the stuff you get told in highschool and forget (in my case). My 
background is mathematics/physics and that's the direction I'm aiming 
for: Starting from why there are 12 semitones to the octave to an 
abstract view on what music "is" (if that's possible at all). I have no 
problem reading hardcore theoretic stuff, but given my lacking 
background I'd prefer a book that's not too hard to read (but still has 
a not-to-low level on abstractness).

So, am I asking for too much or can anybody recommend me something?

BTW, if this is the totally wrong place to ask such questions, feel free 
to point me to a better suited place.


Regards,
Florian