For any course it is essential that students read at least what is stated as essential, and ideally read more widely than that. The lecture course inevitably follows a particular perspective, and there are always other ways of thinking about things. For this course the essential and main text will be:
DA Patterson and JL Hennessy, Computer Organisation and Design Morgan Kaufman, Second Edition 1998, ISBN 1-55860-491-X.
William Stallings Computer Organisation and Architecture, Prentice Hall, 2000
R.E.Bryant and D.O'Hallaron Computer Systems - a programmer's perspective, Prentice Hall, 2003
R.D. Dowsing and F.W.D Woodhams Computers from logic to architecture, Chapman and Hall, 1990, (£14.99).
A book that treats certain topics in greater depth and adopts a distinctive approach (that led to the modern RISC architectures) is
J.L. Hennessy and D.A. Patterson Computer Architecture: A Quantitative Approach, Morgan Kauffman Publishers, 1990. This is a more in-depth version of the recommended text book.
There are interesting popular magazines available devoted to specific systems (such as PC or Macintosh), and in particular the magazine BYTE covers general issues for so-called "small computer systems".