The39clues* is a fun website because you get to be a part of the story and can play fun games. The downside to this site is that it's so sad how in today's world, we feel like we have to attach the internet to a book. I feel like books should just be for reading and the internet should just be for the internet. This webstite tells you that you can win prizes but it's virtually impossible unless you spend your whole life playing a stupid game on the internet, trying to get a high score.
A great website that is fun to do, along with reading the books. I think this is good for kids 7 and up, IF they can do a good amount of reading. For fair readers of 7 or younger have a older sibling or parent to help; or better yet wait a while for them to have better reading skills, so that they can read. Also, there are a lot of stuff that involves the cards and books you have to buy, and some of the later missions get more difficult and stressful.