Recommending books for introductory differential geometry I was wondering if anyone could recommend some books for studying topics such as abstract manifolds, differential forms on manifolds, integration of differential forms, Stokes' theorem, de Rham cohomology, Hodge star operator? Our text is A Comprehensive Introduction to Differential Geometry by Spivak, but I think this book is very difficult for a beginner to learn.
Thanks in advance.

In that you mention "intro," here is a link to an excellent book on differential geometry (free download) about 1/3 down Prof. Shifrin's homepage. It is quite highly regarded and clearly written for self-study:
http://math.uga.edu/~shifrin/
