Linear systems analysis

I first read this book in 1989 when I was in college. Like every college kids, I hated this book, talking about all kinds of boring maths and definitions and theories which were meaningless and useless to me.Surprisingly after 15 years, being a system architect of wireless products in the semiconductor industry, I still find myself going back to this book from time to time in search for answers to some fundamental questions.I would strongly recommend this book for the topic of general linear system analysis.