I like the expression so. Much. The puppydog eyes are killing me. <3 It's really good!
The only two big things that I notice that don't scream BooDog to me are the nose and the shade. The nose seems like it should be larger, both because Boo has a pretty large muzzle and because the eyes are exaggerated a bit larger, which in turn makes the nose seem even smaller. I'm thinking it might be a perspective thing, too - her nose is closer to us, but seems very small?
About the black/shade levels - she definitely needs some more black, but I admit to not being very good with black subjects in B&W art pieces (something I also need to practice). Maybe Laur or Bax might have some advice on that front, they both do it better than I do!
I love it, it's adorable, as I said.
Pencil is a really enjoyable medium, I should really use it more as well.