I'm trying to get my hands on http://www.amazon.com/Computer-Systems-Programmers-Perspecti... but it's quite expensive so I think I'll try to get the 2nd edition.

I've also quite enjoyed https://openlibrary.org/books/OL2197699M/Peter_Norton%27s_as... but you may want to repair the damage caused to the book by the Adobe DRM - it appears only one person can read the book at a time.