I do not recommend Cooper's book. The explaination of the
patterns are not clear. You can not study this book alone.
If you study this book with GoF book, then I assume it brings
no harm, but it does not bring much extra either.
Alan's approach is better: the design pattern are applications
of object-oriented principles, not separated gems. It is a
good introductory book, although it does not cover all GoF patterns.