My ten-year-old daughter, who likes the Diary of a Wimpy Kid books, also liked the Happy Potter books, the Hunger Games trilogy, and the Percy Jackson series.
There are some quite difficult sections in the Hunger Games books, so I read the first one before she did so we could talk about any issues. She’s ten in age, 13 in size, 15 in maturity, and 48 in cynicism; for lots of ten-year-olds the Hunger Games might be a bit difficult/heavy – it is about children killing each other as part of a totalitarian regime, after all.
I’m trying to get her to read the Wee Free Men books, but I like Pratchett and therefore anything he’s written is instantly uncool.
Philip Pullman might be worth a look, too.