(3) Base Camp
We said that The Lightning Thief rested at Sea Level (a 2 on the ol' tough-o-meter). Blood of Olympus is a step up the mountain—the mountain in this case being the Acropolis, the final destination for our heroes. Percy and his pals are a little older, a little wiser, and thereby have a larger page count and a bigger vocabulary than they did back in the Camp Half-Blood days.
One thing that hasn't changed since those times, though, is the fast page-turning pace of this adventurous novel.