Now that was a WIERD book (Slaughterhouse Five)....but must reading...
Personally, I think there's something to the idea of time being ultimately non-linear, though Greene obviously doesn't think so, nor do any of the string theorists. If time is one-deminsional, it can't be anything but linear.
If the time is curved, then it might be non-linear, though I dont know if that would require multiple time dimensions or not.