@boomerang,
I haven't read that one. Sozlet likes the Wimpy Kid books, I haven't seen that one though... I'll ask if she has.
I think that's kind of the Wimpy Kid claim to fame -- don't do the after school special uplift/ moral, be real and sometimes unsavory.
I get why it'd upset Mo, though. I was really upset when I heard a similar story from someone I know well. (They adopted the dog, it didn't work out, they "returned" it. Ack.) At least the dog stayed in the family.