What about the books of Jenny Nimmo?

if your a harry potter fan and like books about young people and magic, Dianna wynn jones is certainly an author to try.

Extremely funny, dark in places, with a wonderfully offhand writing style, and genre that spans world hopping fantasy, to steampunk, to modern fairy tales, often taking into account some wonderfully weird ideas along the way.

For something Ya her Crestomancy series are worth a look, starting with either Charmed life (going in publication order), or lives of Christopher chant (going in chronlogical order), about an enchanter whose job it is to keep peace around related worlds, including his own, which is sort of like an edwardian version of Britain with steam trains and magic, and occasionally touching on our world.

For something a little older there is her castles series, famously beginning with howl's moving castle (yes, the basis for the Miazaki anime, though the books are very different), a bit mor Ya romance and less of the magic, but worth reading none the less.

My lady and I also just finished her book deep secret, one of only two adult books she wrote, since she tended to believe that books about magic couldn't be aimed at an adult audience (sadly she predated Harry potter), that, along with a sudden wild magic are both also really good, though rather more scatty than most of her output.

If you wanted something a little darker, I can recommend Susanne collins hunger games. yes, these are dystopia rather than magic, but deal with many of the same themes, and work in a much harsher way, albeit be prepared for some shocks and violence and bloody evil monsters.

thanks.
someone told me that there was another Percy Jaxen series.
that's Percy Jaxen and the olympians, and there's another one I don't know about

if your going straight from Harry potter and percy jackson, I'd probably not recommend diving straight in to something like Sanderson's mistborn series, much less stormlight, since they're possibly heavier than your looking for.
Skyward is a good bet though, being fast pased and scifi, about a rather hilarious girl living in a society on an alien planet constantly under attack from invaders who finds a special starship ai as her companion.

You might also like Reckoners, sort of silly fast pased stuff about evil versions of super heroes who take over the world.

if you like that sort of thing from Sanderson, then maybe go on to his other stuff and see how you find it.

really recommendation michael scott

At some point I think you should read the stormlight archive, though it is more intense than Harry Potter. The books are quite long, but look at each book as a collection of books. Brandon mull came out with the dragonwatch series, which was basicly a continuation of fablehaven.

I dont know how old op is, but I think stormlight would be appropriate if he was like  above 13-14. There isn't inappropriate content like too many sex scenes or  such. The series does start slow due to worldbuilding, but it  gets very epic beyond a certain point.  Especially in the latar half of book1, and the other books, it has many epic scenes, as well as battles.  But the happiest scenes I think are scenes  where a main character discovers something about themselves or the world,  or  reaches acceptance of some aspect of themselves.
I did read mistborn, though first era so far, it seemed alot more shallow in character development  and more mediocre compared to stormlight, though that probably was because it was written before the stormlight books.

I would suggest Alcatraz and the evil librarians.  It's a good way to get into the vibrant worlds and characters of Brandon Sanderson without diving into something like the Stormlight archive, and it follows the same young male magic user trope of the Harry Potter and Percy Jackson series.
It's a bit sad at times, but also quite funny.  It's a young adult book probably aimed at mature 14-year-olds approximately, but I read it at 23 and still enjoyed it.

If magic is the theme, I'm just gonna throw a couple things at the wall here. lol
The Mortal Instruments by Cassandra Clare.
The Dresden Files by Jim Butcher.
The 20-sided Sorceress by Annie Bellet.

You might like Skulduggery Pleasant. I personally think it blows Harry Potter and Percy Jackson out of the water! It's about a living skeleton who teams up with a 12-year old girl called Stephanie Edgley. They're mainly trying to keep evil sorcerers and gods from destroying the world. I recommend checking out the first 3 books just to see how you like it. It combines humor, mystery, and fantasy very nicely, and the books get better as you progress. The first 9 books are awesome! The newer books are okay as long as you ignore the political correctness bullshit Derek Landy shoehorns.

The Young Wizards series by Diane Duane isn't bad either. I've gone through the first 9 books and am trying to decide if I want to read 10. I like the concept of combining magic with the science of the universe, but they get harder and harder to read starting with book 6 as has been said.

@21, er,
he speaks the truth.
well actually I will be 17 this year.

The Percy Jackson books are connected to 2 other series The Heroes of Olympus, and The Trials of Apollo so you're not done yet. There's also Magnus Chase and as someone else mentioned the Kane Chronicles. I also suggest The Inkheart trilogy by Cornelia Funke, The Bartimaeus Sequence by Jonathan Stroud, and Septimus Heap by Angie Sage. Also Ready Player 1 and Ready Player 2 by Ernest Cline. If you want something darker check out The Red Rising Saga by Pierce Brown it's not complete yet but there are 5 books so far. Also Chaos Walking series by Patrick Ness.