I've read it before, and I had a lot of problems with it. I was in fact discussing it with a friend just last week. Some of the worst laws I've seen:
7. Get others to work for you, but take the credit.
Yes, but only if you make sure NOBODY finds out. To be known as a "credit-thief" loses you friends and associates very quickly. However, its not really a wise move; whoever did the work is bound to find out, and then rumours spread.
12.Use selective honesty and generosity to disarm your victim.
This implies you only be honest and generous when you have a 'victim'. I think your ENTIRE personality should present honesty and generosity - not just when you have to backstab someone. Remember that Stalin used to give food to a local family every week.
17.Keep others in suspended terror: Cultivate an air of unpredictability.
By doing this, you are not setting pre-defined limitations, and it could result in dissatisfied employees (if you happen to be a manager or executive). I certainly don't want to work with/under someone who could get me fired for no particular reason. Most intelligent people prefer to know the limits which you set. Even "Chainsaw" Al and Jack Welch set clear limits.
The worst annoyance I have with the book is the naive tone it was written in, as if following all 48 laws is that simple.
The best advice I ever got was "Always examine the advice of those who are all talk and no action". Robert Greene doesn't have any sort of credentials to back his words; if he followed his own advice, he should either be wealthier than Bill Gates, or at least in some powerful position in business or government. And he wouldn't be sharing his secrets until retirement either =)
People like Robert Kiyosaki, Jack Welch, Deng Xiao Ping, etc have written works, backed up by their achievements. "Walk the talk", I believe, is a common American expression to describe it.