This textbook, aimed at beginning graduate students, is the first to survey the subject emphasizing the role of bijections. ... The final chapter contains a potpourri of delightful results ... The exposition is careful and deliberate, and leaves no stone unturned ... a welcome addition to the literature and a very nice book.-David Callan, Mathematical Reviews, 2012dA rule I have found to be true is that any bookclaiming to be suitable for beginners and yet leading to the frontiers of unsolved research problems does neither well. This book is the exception to that rule. ... I found this book engaging.Abstract: This textbook, aimed at beginning graduate students, is the first to survey the subject emphasizing the role of bijections. ... The final chapter contains a potpourri of delightful results ... The exposition is careful and deliberate, and leaves no stone unturned ... a welcome addition to the literature and a very nice book.-David Callan, Mathematical Reviews, 2012dA rule I have found to be true is that any book claiming to be suitable for beginners and yet leading to the frontiers of unsolved research problems does neither well. This book is the exception to that rule. ... I found this book engaging