(3) Base Camp
The Lost Hero is fairly long, and it has a lot of references to Greek and Roman mythology, so it's a little higher on the tough-o-meter than the very bottom of base camp. But overall, the book is a thumping, highly-engaging page turner with plot, plot, plot, and more plot to rush you along. (Oh, and all those mythological references are carefully explained. If you see a name you don't recognize, just wait a page, and Riordan will tell you all about it. Or turn to the index of Gods at the back of the book, which has a lot of helpful information.)