Roger Young has a great free PDF on how computers work “This is a tutorial web book. All 152 pages of the large paperback book with 96 diagrams are on 38 web pages here. Even if you know nothing about electronics, you have come to the right place. If you are wondering how microprocessors work, you have come to the right place. A microprocessor is a small processor. If you already know something about electronics, don’t be put off by the fact that the book starts out very simple and uses relays instead of transistors…” [via] Link.
How computers work (PDF)