if you liked percy jackson & the olympians...

Iris, Messenger by Sarah Deming
Iris is astonished to discover the Greek gods are all living nearby.  She is even more surprised to learn they need her help!

Theodosia and the Serpents of Chaos by R.L Lafevers
Theodosia's dad runs an antiquities museum, her mom is an archaeologist, and Theo is the only one who can detect and remove the curses from the ancient Egyptian artifacts around them.

Odysseus in the Serpent Maze by Jane Yolen
In the first book of the Young Heroes series, clever Odysseus and his crafty friend Mentor find themselves in a fast-paced adventure involving pirates, a satyr, a 100-headed serpent and a daring rescue.

Sea of Trolls by Nancy Farmer
After Jack and his little sister are captured by Viking Berserkers, they are sent on a perilous journey to the kingdom of trolls.

Ruins of Gorlan by John Flanagan
Choosing Day is quickly approaching and young Will hopes to enter Battleschool. Instead he becomes apprenticed to the mysterious Ranger and discovers the job is more dangerous and worthwhile than he ever imagined.

The Akhenaten Adventure by P.B Kerr
After twins John and Phillipa have their wisdom teeth extracted, they discover they are descended from a tribe of Dijinn.  Now it's up to them to save the world from the ancient Egyptian pharoah, Akhenaten.

Raven's Gate by Anthony Horowitz
As the Gatekeepers series begins, 14-year-old Matt finds himself in the wrong place at the wrong time.  He winds up in the remote town of Raven's Gate, an ancient portal to a world of evil.  Will he be able to survive?

Skulduggery Pleasant by Derek Landy
When twelve-year-old Stephanie's uncle passes away, she inherits his estate and must work with Skulduggery Pleasant, a skeleton mage, to save the world.