Packt publishing, quite an interesting publisher with books very specific (open source) software, has released a book about phpBB. Now that alone is worth a mention. I've had the honor of being a technical reviewer for the book. I received the book about two weeks ago from Packt, but I haven't really had time to do a check of the whole book. However, it does look quite good.
Of course, the coolest thing of the book is the credits page:
It is sooooo cool to see your own name in print, in a book!