Percy Jackson and the Olympians
If you like the Percy Jackson and the Olympians series, then you might like:
Gregor the Overlander, by Suzanne Collins
When eleven-year-old Gregor and his two-year-old sister are pulled into a strange underground world, they trigger an epic battle involving men, bats, rats, cockroaches, and spiders while on a quest foretold by ancient prophecy.
Theodosia and the Serpent of Chaos, by R.L. LaFevers
Theodosia Throckmorton has her hands full at the Museum of Legends and Antiquities in London. When Theo's mother returns from her latest archaeological dig bearing the Heart of Egypt, Theo learns that it comes inscribed with a curse so black and vile that it threatens to crumble the British Empire
Fablehaven series, by Brandon Mull
When Kendra and Seth go to stay at their grandparents' estate, they discover that it is a sanctuary for magical creatures and that a battle between good and evil is looming.
Zeus: Kings of Gods, by George O’Connor
Though raised to enjoy a life of leisure, Zeus must fulfill his destiny and lead a new race of gods--and he must begin by destroying his own father.
Tales from the Odyssey, by Mary Pope Osborne
The one-eyed giant; The land of the dead ; Sirens and sea monsters
The Cryptid Hunters, by Roland Smith
The Siren Song, by Anne Ursu
Thirteen-year-old Charlotte must rescue humankind again when the evil Philonecron captures her cousin Zee, and Poseidon himself sends a sea monster to eat the cruise ship on which Charlotte's parents are trapped.
Jason and the Gorgan’s Blood, by Jane Yolen
Jason, who will grow up to become the head of the Argonauts, leads five other boys on a dangerous quest to save the kingdom of Iolcus, learning along the way what it means to be in command.
Odysseus in the Serpent Maze, by Jane Yolen
Thirteen-year-old Odysseus, who longs to be a hero, has many opportunities to prove himself during an epic adventure.