I agree with those saying the wrap-up is too pat, but I'm surr that comes down to me being in the minority who was into the central concept of this idiot couple story and wouldn't have minded an extra volume. Clearly the result of a need to end the series quickly, presumably because the cries of "how is there no progress" was the voice of the mainstream reader of the story.
A shame if only because the conclusion had so little room to breathe