Wolfborn by Sue Bursztynski
If anybody knows how to write for younger readers it's Sue Bursztynski. The French medieval tale Bisclavret has been adapted and extended out nicely to novel length here, which hopefully encourages readers to do a little research into folk literature and also set them on the pathway to longer length works.
Romance, medieval castles and keeps, an enchanted forest, the faerie world with Celtic-like Gods and of course werewolves (the good bisclavret and an evil loup- garou) make for an enjoyable and gripping read with the language suitably targeting young adults.
I had the good fortune of meeting Sue earlier this year in Perth and there are few around who know folk and fairy tales as well as her. Sue has utilised her bottomless well of folk-knowledge to great effect here with Wolfborn.