Simon Haykin was a Canadian electrical engineer noted for his pioneering work in Adaptive Signal Processing with emphasis on applications to Radar Engineering and Telecom Technology. He was a Distinguished University Professor at McMaster University in Hamilton, Ontario, Canada.
Do not read this book for your introductory course in Signals and Systems. The book is long, verbose, difficult to read and containing unnecessary information (say tons of problems on electricity circuit). You should go for "Schaums Outlines: Signals and Systems".