December 21 is of course the Solstice, the day Percy was supposed to return the lightning bolt to Mount Olympus, so the timing couldn't be more perfect.
The Brazilian edition of The Titan's Curse came out in October, and The Battle of the Labyrinth comes out in January.
Thanks to all the Brazilian readers who have supported the series! I wish I could visit you in person, but alas I have to keep writing the next book. I will be following along virtually, though, to see how the contests go. Enjoy Percy Jackson Day!