DESIGN PATTERNS BOOK ELEMENTS OF REUSABLE ORIENTED OBJECT SOFTWARE

If I am being real, as a programmer you don't really need these concepts when working alone. But these are a must have if you are working in a team

The authors are computer scitienst and its very hard to understands. I basically get sleep than the concept while reading this book . So I shifted to Head First design patterns , it's easy to understand and very practical and simple examples.