Book Challenge Day 4- Favorite book of your favorite book series

I wrote that Percy Jackson was my favorite series.  And, I am going to have to say that although I love each of the books in the series, The Last Olympian was my favorite book. 

This book just wraps up the entire series nicely.  The only loose ends are specifically placed there to introduce a new plot and adventure for the subsequent series.  The characters developed well, and I liked seeing their growth from the first book to the end of the series.