It's a link to the website for Trenton Lee Stewart's Mysterious Benedict Society series, and my first thought was, why don't other books have a site like this?
It's pretty neat -- admittedly I've not tested out the games, but the character quiz hooked me. It's rather an easy quiz to rig, if you're aiming to be "most like" one of the kids, but it's still fun.
Now, a word of caution: it's not accurate.
It is NOT accurate.
I tried to be completely honest when I answered the questions, and it IS NOT ACCURATE! (smolder...) Which character was I? Answer partially copied below:
Nope. SO not me.
But it was fun. Check it out! http://mysteriousbenedictsociety.com/
**For the record: last time I checked it, it was fine -- but it's not my site, so I'm not responsible for the content. I checked it out, I liked it, I'm passing it along because it was fun.