Ohhhh I don't know!!! They were and are so fantastic! I wish that Harry Potter had more books and I wish the next Heroes of Olympus book would come out faster! Of course, the 39 clues isn't over yet, and it is still equally as exciting as the rest of the series. Ultimately, if I had to pick one, I'd say Harry Potter.
Harry Potter is definitely the best story lines, plots, and characters. Some still insist that they dont like it because JKRowling has a habit of sort of rambling on alot, making her books very long, but it is obvious by all the success of the books that 90% of people think otherwise. Percy Jackson didnt really have the grand and epic finale that harry potter did, it was a really good series, but for nine year olds. The 39 Clues are amazing in other ways, with the realistic-ness and present context, but it is not as well-written as Harry Potter. If the books were twice or three times the size than maybe, but this is where the series lacks. Harry Potter has the largest, most detailed, made-up world I have ever read about, with everything from Booger flavored beans, to Dementors and Azkaban. There are so many different storylines, that all meet up in the end. There is soo much intelligence and cleverness from the characters, and plot.
I read a lot of good literature(Dracula and The Odyssey and so on) and Harry Potter has the same type of wording and sophistication as say... Frankenstien by Mary Shelley. All of you haters don't understand proper literature. Percy Jackson would be #2 on my list and The 39 Clues isn't even on the top 3 list.
I have to say Percy Jackson. I can't stop creating them. I've never even thought about drawing the Harry Potter ones and meant to sketch up some 39 clues; but no. I even make little worksheets for my younger friends if they are bored, all based on Percy Jackson. Though I must say I wish Artemis turn Percy into a jackalope for JUST A MINUTE so we could call him Percy Jackalope:) But no. *sigh* I must say if i had to grade these books it would be:
Percy Jackson and the Olympians: 312% The King Must Die: 100% 39clues: 99.8% Chronicles of Ancient Darkness: 98% The Outsiders: 95% Harry Potter: (hard) 90% Lord of the Flies: (a weird) 79% (B--)
I'd put more down by the authors on 39 clues but I have yet to read any of their books! Oddly enough I'm a very busy person!