Trying to figure out heat of reaction
There is a "readme" note from the author that says:


  The answers are not guaranteed, in the sense that not only
  might I make a mistake here and there, but I might have used different sources of
  data, or the data in a database may have changed. I have not been able to check all
  the answers, or to make them all consistent with the data in Appendix B, although I
  believe that most are.


So I think that this problem is an example of one of those situations.  

The book itself works out the problem on page 267 and gets the same answer as you: −12306 J/mol.