Sometimes, no one wants certain math books. Then, you can get them really cheap.

I've got this one coming for $8, including shipping.

http://www.amazon.com/Complex-Variab...3374207&sr=1-3

(A long time ago, a teaching assistant who I had for a math course, and who was getting his Ph.D., basically told me that he thought it was very difficult for a person to learn math without talking to other people. My experience has been that he was correct. Sometimes, I can't figure out how an author did some calculation, and, there is no one to ask. My psychological tendency is to just stop there. But, that way is very bad, you never advance. It's much better to look for other sources, or just to try to continue on, and let the frustration go.)