The first 15 years of Personal Computers (PC) are trivialized by Cringely, which is hard to do, since he wrote this entire book on those years. Basically, just imagine someone writing a history of the PC while hoping it might be a multi-page excerpt in the Rolling Stone.
Silicon Valley represents a great deal of massively compressed work. Jokes about junk-food-filled programmers operating on caffeine and 2 hours of sleep leave the reader with the false impression that it was all "just a matter of programming", and that the real work was done by high-octane business types.
In reality, there was a bit of serendipity, but there was always a slew of people working their butts off to beat out the competition. Programmers, engineers, and businesspeople all worked together to get the job done. In the end, the businesspeople usually got most of the money, but that's what happens when you let someone else write the contract.
Perhaps the best idea of the book is to show people that startups do work, and to show the difficulties of previous startups. From all of his research, Cringely has three tips for start-ups: