I think I picked these books out of an NPR Book Review page, probably something listing a bunch of young adult/science fiction and fantasy titles - I can't think where else I would have found them. They aren't new books - Alanna is from 1983; and Sabriel is from 1995.
Alanna: The First Adventure - by Tamora Pierce. When their father decides to send them off for training, eleven year old twin, Alanna and Thom, hatch a plan: tomboy Alanna, who wants to be a knight, will disguise herself as a boy and go off to learn sword-fighting, horsemanship, chivalry and the lot, while her brother Thom, who has a facility for magic, will go to school to learn to be a sorcerer. Young "Alan" makes friends - and enemies - quickly at the castle, and throws herself into learning how to be a knight, showing remarkable skill with a sword; she is also unable to entirely distance herself from magic, and once she saves the prince's life, she becomes entangled in palace intrigue. As the title suggests, the book follows Alanna's exploits, only barely checking in on Thom, following her through the first couple of years of her training. This Alanna book, the first in a quartet, is written for very young adults, or better yet children. The writing is not particularly sophisticated, the characters are not well developed and the plot seems written in rather broad strokes. I've read children's fantasy that are clever, intriguing, well-written and intricately plotted - this is not one of them.
Sabriel by Garth Nix. Sabriel is a particular kind of sorcerer, an estranged native of the Old Kingdom and daughter of the Abhorsen, trained to go into Death, ushering lost souls into the light and keeping Death's more gruesome denizens from overrunning the earth. On her eighteenth birthday, she was supposed to meet with her father; he never shows up, instead sending a messenger to her with his enchanted tools and bells for safekeeping. Sabriel enters the Old Kingdom, on a quest to look for him. Along the way she makes some strange acquaintances and good comrades, and ends up wading deeper into Death than she ever has before. I liked Sabriel more than I did Alanna, but again, this book seems lightweight (despite all the death and destruction and scary scenes) somehow. It switches point-of-view oddly a couple of times, which was distracting enough to pull me out of the story, and the characters are pretty thin.
12 hours ago