I heard good things about Combinatorics and Graph Theory by  Harris, Hirst  and Mossinghoff  (Springer Undergraduate Texts in Mathematics).

It's easier to read than Diestel or Bollobas, but not dumbed down. But of course, it's neither thorough nor exhaustive.

What introductory book on Graph Theory would you recommend?
I am making a 2d tile based game in C# and XNA 4.0. I am having trouble loading and unloading "chunks" of tiles(blocks). The whole world is randomly generated and is infinate on both axis. How would I go about loading and unloading chunks of tile data in the camera's view?

A pastebin to the pastebin links(I still have the 2 link cap):

http://pastebin.com/9PYr8cvC
