I didn't make notes as I read this series, so this reaction/review thing is straight from memory. Also, it says something that I didn't make quote-notes on these books. The writing was straight-forward and efficient, but no elegant prose or inspiring quotations were found here. The series is written for a younger audience (I found half of the books in the children's section of the library with the other half being YA...disorganization, anyone?), but I enjoyed it just fine.
At first, Percy's lack of common sense annoyed the piss out of me. I think even I had more common sense at 12, and he's a demigod (half god, half human)! The kid seemed incapable of drawing conclusions no matter how much evidence was slapping him in the face. Typical scenario: weird crap happens, weird crap, weird crap, and Percy concludes that weird crap isn't really happening. Okay, now repeat that at least 15 times. That was really my only major gripe I think, besides the reiteration of scenes to remind the reader what happened in the previous book. I got it, thanks.
This series is rooted in Greek mythology and there are a lot of characters. We meet all of the Olympian gods, most of the Titans, plus a hundred or so minor gods/demigods/monsters.
Side note: We had a game night at Ashley's recently and reading this series helped me answer a ton of questions about Greek mythology. It delves (at least briefly) into many myths, with enough visual description to lock them into my brain.
I don't like giving too much away if I can help it. Basically this series is about a 12 year old half-god coming of age, while also coming to terms with the fact that Greek myths are reality, his father is Poseidon, monsters are trying to kill him daily, there is a summer camp for demigods to learn how to stay alive, and there is a prophecy involving him that might just determine the fate of humanity. No big deal. So yeah, it's okay...not my favorite series, but not my least favorite either *coughHisDarkMaterialscough*
Ratings:
The Lightning Thief 7/10
The Sea of Monsters 6/10
The Titan's Curse 7/10
The Battle of th Labyrinth 8/10
The Last Olympian 6/10