Garth Nix

"There is often trouble of a mythical sort in Bath. The booksellers who police the Old World keep a careful watch there, particularly on the entity that inhabits the ancient hot spring. This time trouble comes from the discovery of a sorcerous map, leading left-handed bookseller Merlin into great danger, requiring a desperate rescue attempt from his sister, the right-handed bookseller Vivien, and art student Susan Arkshaw, who is still struggling...

Seven days. Seven keys. Seven virtues. Seven sins. One mysterious house is the doorway to a very mysterious world -- where one boy is about to venture and unlock a number of fantastical secrets. --from Amazon. Arthur Penhaligon is supposed to die at a young age, but is saved by a key that is shaped like the minute hand of a clock. The key causes bizarre creatures to come from another realm, bringing with them a plague. A man named Mister Monday will...

Odo is the seventh son of the village miller and he just wants to get away from work for awhile, Eleanor's mother was a soldier, and she yearns for adventure, but it is Odo who finds the magic talking sword named Biter, and thereby instantly becomes a knight--and together they set out on a quest (somewhat reluctantly on Odo's part) to save their kingdom from threats both human and dragon.