Anyone see He's Just Not That Into You, or read the book? What's your opinion?

Do you believe that men aren’t complicated, that their actions can only be explained by either ‘he likes you’ or ‘he’s just not that into you’ or do you stand by the belief that like women, like human beings, men have layers and do things that can be explained with more complicated reasonings?
Is it really smart to think that if a man does something that seems like he’s not interested, it means he isnt?
Does this rule only apply to non-serious dating or do the creators believe this to apply to long-term relationships as well?