The two books below are good books regarding aerodynamic theory and application. Fundamentals of Aerodynamics is heavy on theory, but it can better explain "where lift comes from," and Introduction to Flight is a great book regarding applied aerodynamics and aircraft performance.

[link=http://www.amazon.com/Introduction-Flight-John-D-Anderson/dp/0071263187/ref=pd_bbs_sr_1?ie=UTF8&s=books&qid=1221785734&sr= 8-1]Introduction to Flight[/link]

[link=http://www.amazon.com/Fundamentals-Aerodynamics-John-D-Anderson/dp/0071254080/ref=pd_bbs_2?ie=UTF8&s=books&qid=1221785734&sr=8-2]Fundamentals of Aerodynamics[/link]

Lift force is generated by pressure differential between the top surface and the bottom surface of the wing. It is not one or the other.

I have the fourth edition of "Model Aircraft Aerodynamics," and a very nice, cut and dried explanation of how an airfoil generates lift is given in the beginning of the book.