I really, really wanted to like this, as it's such an interesting and fun idea - but I just didn't. So many other reviewers loved it that I am reluctant to put anyone who is thinking of buying it off in case it's just my personal taste.
I can tell you why I did not like it: I agree with the other negative reviewer - this book is not really kind to it's central characters. It mocks them quite a bit, and they are all stereotypical and two-dimensional. I didn't feel we really got close to them, as we were buffered from them by the quite 'heavy' voice of the narrator, which overshadows everything.
In fact, I think the 'book' narrator was a big part of the problem for me. I found it really pretentious and overly verbose in places. Its ramblings often take you away from the action of the story, and not really in a good way, unless you like congratulating yourself about your ability to appreciate endless puns. The writer is very creative, I'll give him that, and comes up with some great analogies - but sometimes you wish he would stop showing off and get on with the story. I would have preferred a switched narrator - i.e. sometimes the book, sometimes the characters. That would have made it more enjoyable for me.
I liked the old book itself, the one by the fictional author, and I thought it made some interesting and though-provoking points...but you only get the odd page now and then in a slightly jarring way, and it's an odd combination of different styles.
Most of all, I did not like the toilet humour in this book. I am very squeamish about reading horrible things in graphic detail and some of it literally made me so nauseous that I had to scan pages to get the end of the scene.
So, if you are squeamish like me, don't read this book! If, however, you don't really care about getting close to the characters, find toilet humour hilarious and you like the idea of endless puns and some genuinely creative analogies - then you might really like it.