This is a poorly-written, largely unhelpful, book that spends too much time on the obvious, while glossing over the difficult. What it lacks in substance it makes up for in fluff, the diagrams/illustrations being the worst offenders. One of the most pointless is Figure 5-4, which takes up a third of the page to illustrate a “ten-button keypad lock” as ten circles, each containing a number from 0-9. There are other equally pointless illustrations throughout. The most useful part of the book is Appendix A, which explains patents and patent laws.