Gwen and Art Are Not in Love by Lex Croucher

SIGNED

Gwen, the quick-witted Princess of England, and Arthur, future lord and general gadabout, have been betrothed since birth. Unfortunately, the only thing they can agree on is that they hate each other. When Gwen catches Art kissing a boy and Art discovers where Gwen hides her diary (complete with racy entries about Bridget Leclair, the kingdom's only female knight), they become reluctant allies.

By pretending to fall for each other, their mutual protection will be assured. But how long can they keep up the ruse? With Gwen growing closer to Bridget, and Art becoming unaccountably fond of Gabriel, Gwen's infuriatingly serious, bookish brother, the path to true love is looking far from straight ...