Head First Design Patterns by Eric Freeman, Elisabeth Robson, Bert Bates, Kathy Sierra is really a wonderful book to start learning the design principles of OO Programming. The book is interactive and that there is ver little chance that the reader will be bored. I got this book from Flipkart for Rs.469/-
This is a link to the scanned copy of the book.
http://adf.ly/BzxnF
But my suggestion is to buy this book. Its a good book to refer all the time.
If the link is removed or broken notify in the comments section :-)
