A Prince Among Frogs — Elisabeth Waters

Be careful what you wish for ... Jan, a stage magician, wants a new act for her show. Florian, a prince, wants to be a hero, so he sets out to rescue a princess abducted by a dragon. But Princess Rowena doesn't want to be rescued, so Florian is suddenly thrust into Jan's world, where he keeps changing back and forth between frog and prince. It's up to Jan to figure out the mechanics of the spell, and then take advantage of it to help both of them get what they want.