Seems to be a lot of secrets about these days, we have Steve Chalke's 'Lost message of Jesus', which is kind of secretive, unless someone found it, and now Brian McLaren's new book 'The Secret Message of Jesus'.
I guess all these authors are posing the idea that if so many people don't know Jesus and mission with Him, they must have missed something, or christians might have lost/misplaced/not found something that we should be sharing, or know about.
So I just bought Lesslie Newbigin's 1978 book, 'The Open Secret'. What an outstanding book on the Kingdom, Church and Mission. But make sure you don't tell anyone about it...sssh.