It sucks you in. It's strange, confusing at times, and you must know what happens next, so you keep reading.
So Ukiah was largely oblivious to the opposite sex until he met Indigo. This had the side effect of hurting a friend who was apparently waiting for him to grow up (uh, that could take a while, seeing as how he only ages visually when he's severely injured). The friend takes off on a college trip of some sort and is kidnapped. Why she's kidnapped... I didn't really get. She found things about his past, but the people who grabbed her didn't know what she found, or who her connections were. They didn't realize what a can of mice (hah!) they were opening by getting his attention and that of the Pack.
And that's basically the story - he and his companions spend much of the book trying to figure out how, who, and why, only to figure out that it's the Pack enemy who apparently grabbed her because of what she was looking at but had no idea that in doing so, they'd get Pack attention.
I have to say, this basic theme only works if eventually there's resolution. There are only 4 books but is that because the series ended or because the author hasn't gotten around to writing more?