The Strange Land Trilogy: Books 1 - 3 by Ben Anderson
The McGunnegals are all strange, and it has been that way for generations. They are too strong, or too fast, or too smart, and odd things happened when they are around. The neighbors say they are witches or devils, or have been snatched by changelings. Mothers hold their children close when they walk by, fearing they might catch the McGunnegal strangeness.
But when a doorway to the world of the Others is found in their great grandfather's potato cellar, two of the children fall through, and find themselves in a land where all of their strangeness will be needed to rescue its people from the dark things that have enslaved it.
There they also discover why they are so different, and also what it means to be truly human.
The Strange Land Trilogy is a compilation of the first three books in The McGunnegal Chronicles series, including "Into a Strange Land", "Taming the Goblin", and "The Witch and the Waking Tree".