Darkhenge by Catherine Fisher
From the book jacket...
"It's been three months since Rob's younger sister, Chloe, fell into a coma after a riding accident, and his life is in disarray. Rob's parents spend most of their time at his sister's bedside, and his best friend is afraid to talk to Rob about Chloe. To distract himself, Rob takes a job working at a secret archaeological site, where workers have uncovered a mystical ring of black timbers. At its center an ancient tree is buried upside down in the earth -- a tree with the power to transport Rob to the Unworld, where Chloe lives in a forest of enchanting dreams, trapped between life and death."
Warrior Girl by Pauline Chandler
From the book jacket...
"Jehanne sat bolt upright in the saddle and held her lance steady. I felt again that stillness of hers and saw that her horse stood quite still, as well, as if aware of the immensity of the challenge. De Baudricourt signaled his men to stand back. The whole company gathered in silence to watch Jehanne ride the list.She looked straight ahead down the field. The other rider waited, the trumpet sounded, the flag dropped, and Jehanne touched the sides of her horse, once, with a powerful kick. Like the destrier he was, he thundered forward, nostrils flaring. His ears flicked back as Jehanne leaned slightly forward to take aim.
Craaaasssh! The two riders met in a cloud of dust and I craned my neck to see who had survived."
