David Brin writes the story tongue-in-cheek (I mean baking yourself a duplicate is kinda outrageous, isn't it?), but without descending into parody or outright silliness. In fact he keeps a straight face throughout the book, and stays on the main theme, which is an interesting mystery tale, sufficient onto itself in terms of story-telling value. (Somehow, this approach reminds me of Vernor Vinge's Marooned In Real Time, a 5-star book based on those absurd bobbles.) Also, Brin doesn't take the extrapolation of the central premise too far, avoiding the pitfall of writing in thousands of additional words of "explanation." All that works for me, though I realize this may be a minority view.
I am somewhat longing for a sequel, but am ambivalent on this. Sometimes, a bad sequel could wreck the mystique of the original. In any case, wholeheartedly, thanks for writing this book, Dr. Brin.