The first book of the series was by Rick Riordan and entitled "The Maze of Bones". It held just enough promise that I reserved and just finished reading "One False Note" by Gordon Korman. I now have book 3 on reserve at the library, "The Sword Thief". There are 10 books in all.
The story surrounds two siblings, Amy and Dan. Amy is a shy, timid 14 year old and Dan is a typical rambunctious 11 year old boy. Several years earlier they were left orphans and have been raised by an elderly aunt. There is also a grama in the picture who is very wealthy, but for some reason she has not been raising the children herself. However, they visit her on weekends and are very attached. After the grama dies some strange requests arise out of the reading of her will and so start the children on their journey around the world looking for the 39 clues. Other members of the extended family are also racing to be the first to get to the 39th clue which will supposedly make them the most powerful person or persons on the planet. This makes for some hairy adventures.
Would I give these books to my avid 11 year old reader? No, basically because the children are constantly disobeying authority figures and getting into trouble and he doesn't need that kind of influence. They call each other disrespectful names and that could rub off.
One aspect of the books so far that I find interesting is the extensive descriptions of the settings that the books take place in. Lots of historical information is added in. It almost makes me think that the books were written to try and get kids to learn something while being taken in by the plot.
You can definitely tell that these books are written for children. There isn't a lot of depth here. Beach reading for sure. However, I want to keep reading to find out the final answer to the quest. I hope I'm not disappointed, but little would be lost as these are very quick reading.