Denise Jaden does a wonderful job on writing the book. At times the book does go slow, but this is not a topic that needs to be rushed.
And since this is a teen book, clearly there has to be some romantic situation. Brie's first boyfriend was a jerk. No need to comment on that one more. But, what I liked about the way the author incorpporated Alis (short for Alistair) was wonderful. Tessa and Alis were definitely round characters. Each of them had their own spying methods to help Brie figure out the mystery of her sisters death and they were usually cool or hilarious.
If you are thinking about reading it: read it. Maybe don't read it all, but read a couple of chapters and then decide whether or not to read the rest. But the book is good.