Sketchbook Peek - Face in Soft Pencil

My sketchbook is full of drawings of faces and sometimes I ask myself why I like to draw them so much.  I haven't figured out the answer totally yet but I think it may have something to do with 'meeting' a new person each time I draw one. I see the personality emerging as I continue drawing and I find it fascinating. Is that weird? Anyway, here's a face that I sketched not too long ago that I really like.  I quite like the effect of the soft pencil I used and it was quite meditative to draw her.

I can't help wondering what she's thinking.

What is your sketchbook full of?  And if you're not an artist, do you doodle whilst on the phone?