Mandatory reading
There is one book that all students should have read from cover to cover before starting the course:
Goldschlager, L. & Lister, A. (1988). Computer Science - a Modern Introduction. Prentice-Hall (2nd ed.).
You should also try some of the exercises. In particular, the first 15 exercises at the end of Chapter 2 on the design of algorithms and the first 10 exercises at the end of Chapter 4 on computer architecture are relevant preparation for the introductory lecture courses.
General reading
An excellent informal collection of accessible and relevant articles can be found in:
Dewdney, A.K. (1989). The Turing Omnibus. Computer Science Press.
Course reading
You might like to look at some of the text books that are listed elsewhere in this document. Printed notes will be handed out for most courses, so you don't actually need to buy all of the books.