It's not like it was his fault! She came a his with claws and talons and all hiss-hiss, give me your soul, you're not getting out of here alive. What was he supposed to do? Actually give her his soul? That's not how Percy Jackson does it. (Plus, those bargains never work out too well for the soul being sold...)
Soon enough Percy found out that he was a demigod (half human, half god). One of his parents (growing up without a father, there wasn't much question) is a Greek god. With Percy bursting pipes and using creek water to heal himself, well... Hello, Percy Jackson, son of Poseidon.
Which, here and now may not be the best thing. Zeus's lighting bolt has been stolen, and the main suspect is Poseidon, considering he has tried to overthrow his brother in the past. The god himself wouldn't do it, of course, but he could send a human hero - Percy Jackson. Percy Jackson who has no idea, what the Hades is going on, and why he's suddenly the bad guy.
Since I already mentioned him, what is the role of Zeus's other brother, Hades, in all of this? Chiron (and the oracle) consider Hades the man for Percy. So the main question remains: can Percy retrieve the lighting bolt (and his mother) from the king of the underworld before all Hades breaks loose?
Follow Percy and his humorous narration throught this series where he tries to die, get a girlfriend, and save the world (and somehow manages all three, without losing his hilarious sense of humor and charming cluelessness).
The characters in this story have special powers, thanks to their godly parents, but they are not perfect. Far from it: most of them have ADHD, dyslexia or both. They have trouble concentrating in "normal people school," because their minds are suited for the battlefield. When they are fighting medusae, giants or any other monsters, however, their ADHD allows them to focus on the many things that are happening all at once.
I really like that Rick shows us that their special abilities, however cool, they may be, bring more trouble than happiness... are more curse than blessing. Of course, they get to learn new skills, and make new friends, but they are all constantly on the run from monsters at a very young age, the only safe place being Camp Half-Blood.
Also, their abilities may spark jealously between the different cabins, which reminds me of the jealousy we have at school over inanimate objects. This could potentially cause some to turn to evil and well... just reminds us that fantasy worlds are not an escape from all of our everyday problems, they just show us the problems in a different light. If we see things from a magical angle, some of us ignore the serious things. We ignore the things between the lines... however, in "Percy Jackson," these things aren't even between the lines. They are right there in the text, so even the most ignorant people pay attention to them.
The main plot in Riordan's book is the adventures which Percy and his friends undertake in order to keep the mortals safe, but the series gives off a strong "troubled teen finds friends" vibe, that I really love. It shows that having special powers doesn't make being a teenager any easier. (AS IF it wasn't hard enough to begin with...)
Many fantasy and sci-fi books published currently try to pull out heart strings, and this one hits the bulls-eye.