Sanderson is quite brilliant. I've read most of his books now and while I think this is aimed at teenagers, I didn't find it childish at all. I enjoyed it and am looking forward to the next in the series. I don't think its his best work, but I wish I had a 15 year old son that I could force it upon because it would be perfect for them. (i'll give my daughter another couple of years and then get her to read it instead).
I liked that the characters didn't just have everything given to them, they had to work their butts off for what they wanted and sometimes that still wasn't enough. There was no super special snowflake that got everything they wanted, just because they wanted it. I think that sends a realistic message about life.
The magic system was seemingly simple, but I admit I had a hard time wrapping my head around it, because seriously what damage could a chalk drawing do to you..... Well by the end I was convinced of the havoc they could unleash. I liked the illustrations throughout.
So in all a solid book and well worth my time.