So, I just finished it. And those books really doesn´t stop topping each other!
I´m a bit disappointed about Josh - he might never have really trusted the Flamels, but I would never have suspected him of leaving Sophie alone with who he believes is the bad guys.
Aoife´s sacrifice doesn´t bother me that much. Characters keep being sent off to certain death in these books, and unlike those which we actually see die, most of them return - think of Scatty´s disappearence, or of all the death-or-victory situations Dee has failed at without ever actually dying.
It did puzzle me a bit, however, that when all the Elders we´ve been presented to so far, even together, would be unable to defeat the Coatlicue, it did turn out suspiciously easy for a single Next Generation to do it.
Anyway, I don´t think Aoife is going to return anytime soon - if she is, probably not before the end of the series, and probably just for the readers' contentment.