Have you read the previous Shadow books (I think there are 3 or 4, ending with Shadow of the Giant)? Petra pretty much gets her entire life arced out in those books, which are honestly not bad except for the supervillain (who needed to die in the first book, but kept hanging on for no good reason for several books after that). I actually did enjoy Bean/Petra in those books. I wouldn't call them Card's best work or anything, but they were still enjoyable and had some political intrigue that I found fun to read.

But this particular book, yeah, there's no point in reading. (And no Petra, anyway :) ) If you'd like I can recap the entire thing right here: Bean's mutant genius kids don't die. The end :)