The book says many things which are true and correct. For instance church buildings are not design for Christian fellowship. They are designed for turning up, not talking to anyone and leaving straight after the service. This is true, most church buildings are not designed in a way that promotes Christian fellowship like what we see in the bible.
Elsewhere, it talks about how scriptures like are misused. One instance is Malachi 3 in regard to tithes and offerings given to the Levite priests to be sacrificed to God. What it states about this subject is more or less correct. Many churches do try to make a direct application of this in the New Testament Christian church today, which is not correct. Christians are not required to give a tithe (but the call to be sacrificial is a reoccurring theme in the New Testament - something which the authors don't seem to mention) and there is no Levite Priesthood in existence. However, where the book falls short is that it doesn't say how Malachi shows the heart of God (after all, Malachi is a book where God has much to say) and offers no New Testament application of these scriptures.
The basis of many of the arguments in the book are based on a flawed interpretation of 1 Corinthians 12-14. The Corinthian church is being held up by the authors as a model church. However, when you read these passages in the context of both books of 1 & 2 Corinthians, the Apostle Paul is far from lifting up the church as an example to be followed. 1 Corinthians 12-14 is more about reigning in the chaotic worship (where people are getting drunk at church for instance) of the church than a model for all churches.
Ultimately, the book is divisive. It doesn't promote love, but division.
It encourages people who read the book to silently leave their churches.
The alternative which it proposes is organic churches, where nothing is prepared (no prepared sermons or lessons) and people share as they feel moved to do. This isn't something that is backed up in the New Testament.
They're aren't too many of these 'organic' churches around (as they are described by the authors) and people reading the book will be left with nothing.