I would say that this book should be read and used more of as a traditional children's story: Don't take it too seriously and you might end up with a good moral at the end. McLaren's problem is that he neglects everything that disagrees with his perspective - and thus loses out on huge (and I mean HUGE) theological necessities of Christianity. If I were to read this book as a strict theological text, I would have rated it a zero (or given it an 'i' for incomplete).
However, if you take this book as simply one man expressing a far-out idea for the purpose of proving a point or getting us to shift slightly more to his angle, it wasn't terrible. I disagree with the very idea of making a hyperbolical viewpoint to force a paradigm shift (think "the earth will end in 5 years" scare tactics to get people to do something reasonable like recycle), but McLaren is much more literature-based than he is scientific method-based so I can look past it.
Long story short, don't take this for what it says. That is, don't take this for what it says if you want to enjoy it at all (without the need to rip your hair out in frustration).