Short version: An entirely satisfactory conclusion to The Kane Chronicles.
Long version here at The Geek Girl Project.
Additional Comments: The end made me smile happily as completely confirms that these *are* happening in the same universe
as the Percy Jackson stories & leaves a tantalizing opening for
crossovers (without actually requiring it). I don't know if I really want a crossover or not. It seems like such a book would be awfully crowded, what with all the gods and heroes available. But thinking about such a crossover makes me very happy, and of course if one came up I'd grab it at once!