I agree with Carl wholeheartedly! There is SO much on the web today that you can learn almost anything. Books are becoming obsolete. (I still love to read though and have quite a few books.
Digital books are aplenty, and many older books can be had for no cost. As Carl said, Lee Hammond is good, and there are many others out there! BTW.. Carl and I met on Duey's forum about 3 years ago.. and there are some really good tutorials out there (Although I think the site has become obsolete now)
Having said that.. There is a plethora of Youtube videos that teach every concept of drawing that you can think of. It's like having your own personal instructor at hand. Another great teaching aid are tutorials on Deviant Art.
Having said all of that.. the best way to learn to draw.. is to draw! I know it sounds blase.. but it's the truth. I got an inexpensive course from Christopher Sia when I first decided to draw and knew nothing... (Was $27 I think) and I drew and drew and drew. I have never looked back.. and I think I am ok (although definitely where I would like to be yet!)