I left the following comment today on this thread— most of the comments are in English but the main article is in Portuguese, so use an online translator if you want to read it.
Today I also received a copy of the book. I believe it is is a clever form of “Christian viral marketing” aimed at intellectuals who have previously written admiringly of the works of Escher, Hofstadter, Adams, and such, as I have done at various times on my blog and other web sites.
As one who was raised as a Christian and then left the faith, the allegorical nature of the work is quite clear, even from the enigmatic “Will tell you more when I return!” (clearly a reference to the Second Coming of Jesus) inscribed on the envelope where a return address should appear, to the book’s closing warning, “You wouldn’t want to trade the eternal loop of your life for an infinite loop in the world of ideas, would you?” (clearly a reference to choosing faith and eternal life over rationality and empiricism.)
Overall, I’m impressed with the author’s willingness to try a new approach to reaching intellectual non-believers by the attempt at creating a faith-based logic-breaking koan. But the message is still the same: if you want eternal life then check your brains at the door.
Update: A good conversation about the book has taken place at Metafilter. The thread even includes links to a scan of the book.