While not confining himself exclusively to the question of 'why are we here?' and referencing the anthropic principle, it is one of the main thrusts of the book. The kernel is that he feels there may be indirect evidence (if not now, then eventually) for a plethora of universes, where the six numbers all vary, with the majority of universes being sterile. Given this, it is not so far-fetched to say, "if our universe was inhospitable, there would be no sentient life to ask why it is special".
Next in the queue: Red Lobster, White Trash, and the Blue Lagoon: Joe Queenan's America. I've got this on request with the library, and found out about it while browsing weblogs. I think I saw it on Kottke.org. The Amazon.com link above contains the quote:
Queenan sets out to find music, movies, books, and TV that transcend awful, and the most remarkable thing about this book is that one never doubts for a moment that he actually subjected himself to all of the horrors he describes (including the literary efforts of Joan Collins).