Depends on what kind of things you want to study a' krub.
I took group theory three times. They are all different

First time it was pure math. Algebraic structure studying group ring etc. I don't have a recommended book for this though. We use lecture notes. It has absolutely nothing to do with physics but fun to learn and prove things though.
Second time I took it from a physics professor, he focused on finite group for crystallography and treatment of Lie group and stuff for particle physics. You can download the lecture note though.
http://www.cithep.caltech.edu/~fcp/ph129/index.shtmlThe third time is pure particle physics application. the book is called Lie Algebras in particle physics from isospin to unified theories by howard georgi. Pretty good book. I don't remember how much I bought it but I think since it's soft cover it should be cheap