Charismatic characters, a deep and involving world, and a great series. Overall, a great book that will surely entertain most readers.
On a personal note. If your thinking about Mark of Athena, give this series a try and you'll quickly be abandoning Rick Riordan.
This is definitely a must read. I had a lot of fun with it and found looking at the world through Brandon was done very well. Things are described as a young boy would see them, which makes for some very interesting descriptions.