What are some useful books you'd recommend to someone looking to get into digital art/fan-art?

Just picked up these two books here

book 1 : http://www.amazon.com/dp/0955153077/

book 2 : http://www.amazon.com/gp/product/0956817165?

I'm experienced in art, I have a little bit of background but I'm not that great at it. I can manage to draw people, but I think I could improve my talent as an artist. I'm looking to improve so I can get into fan-art.

I'm really wanting to be more active in communities I really enjoy but I don't know where to begin. Can someone recommend me some basic text books or intermediate books as well?