I did not read the book, but i did live not far from Rick Warrens church for many years. My close friend, & the person who taught me about discerning bad teachings, & about doctrine, who's opinion i trust 100% in such matters, has been to his church & interacted with a number of attendee's. He is, plain a simple, just another 'make myself happy gospel' preaching megachurch pastor. He stops his preaching half-way through the service to advertise his other ministries. (the church has countless number of groups for varies problems, drug addicts, various illnesses, etc). A lot of emphasis is put on these groups, even during service, almost seeming to trump any other message. And even then the message he gave was very shallow. He calls the church 'seeker sensitive', which in essence means 'we don't want to offend anyone with talk of sin, repentance, hell, spiritual matters, etc.
I also knew someone who lived in a neighborhood with a number of people who attended his church. They were frequently rude & at times even mean to this person. The attendee's children were known to bully. When my friend contacted the church directly to see if they could speak to the families about their behaviour she was told that because she was not a member of the church there was nothing they could do, in spite of the fact that the people being complained about were members.
Lastly, the 'non-offensive' attitude permeates everything they do. Church sponsored services often allow bad attitudes, poor treatment & even bad teaching because they don't want to 'offend' anyone by correcting wrong behavior. Thats all i need to know about before reading any book.