Children of the Lamp: Arkhenaten Adventure, P.B. Kerr
Arkhenaten Adventure is the first book in the Children of the lamp series, in which the twins John and Phillipa Gaunt discover that they are djinn (genie) and that they have the power to grant wishes.
They first discover their new powers when their housemaid (their parents are rich) Mrs. Trump, suddenly wins the lottery, the day after she told the twins that she wished she could win the lottery.
After that their parents decide to send them to their British uncle Nimrod's house for the summer, where they will be trained to be responsible djinn. But Nimrod had other plans. Nimrod decided that they will go on a trip to Egypt, the original home of the djinn, to try to find The 70 Djinn of Arkhenaten so that they can balance the powers of luck with the powers of chaos. The problem is that they aren't the only ones looking for them. John and Phillipa not only have to find The 70 Djinn of Arkhenaten, they have to find them before the evil djinn, the Ifrit, can use their power for their own gain.
I really liked this book because it kind of reminded me of The Kane Chronicles, and because there are a lot of funny parts, for example Nimrod tells John and Phillipa that smoking wasn't actually a human invention, but a method for djinn to stay warm (they are more powerful when they are warm), and the humans just wanted to copy them. 12+ for magic (Nimrod would disagree, he doesn't think of djinn power as magic). I would recommend this book to anyone who liked the Percy Jackson Series, The Kane Chronicles, or The Heroes of Olympus.
Note: My sister Katie, age 15, started to read it and stopped after about five pages. She doesn't like that it's written in the 3rd person and she didn't think it was engaging. She said she will probably try and read it again.