Sad that I've finished the series now but really loved it. I just adore Riordan's writing style. Although some of the humour would be considered immature, it worked so well on the books. I think it was well balanced with great wit. He really brings these myths to life in such an interesting way. With intertwining them in to the modern world in a clever manner, really made it enjoyable to read. 

The story itself for the last book was well layed out and kept me interested throughout. Added bonus that I now have more knowledge about Norse mythology than when I started.

He's a great writer for all ages.